A compendium of male breast imaging: The road less traveled

Abstract

Male breast disorders, though less prevalent, present unique diagnostic challenges that differ significantly from their female counterparts. While benign entities such as gynecomastia are predominant, the risk of underlying malignancy, often diagnosed at an advanced stage, highlights the need for a systematic, image-guided assessment. Ultrasound and mammography are the first-line complementary tools, with magnetic resonance imaging reserved for problem-solving. This review outlines the anatomical, pathological, and radiological nuances of the male breast, describing crucial red flag signs, sonographic pitfalls, and mammographic mimics that aid in distinguishing benign entities from sinister pathologies such as invasive ductal carcinoma. Given the increasing visibility of transgender individuals, this review also addresses imaging considerations and screening recommendations tailored to this population. By integrating clinical insights with radiologic imaging, this review offers a comprehensive approach to both common and not-so-common male breast lesions, with an emphasis on an algorithmic stepwise diagnostic approach.

Key Words: Male breast; Cancer; Mammography; Ultrasound; Gynaecomastia; Transgender; Pilomatricoma; Invasive ductal carcinoma; Imaging; Papillary

Core Tip: Male breast disorders are relatively uncommon. Imaging of the male breast, per se, warrants attention as the radiological findings may differ from corresponding pathologies of the female breast. In addition, red flag signs on mammography and ultrasound must be accurately picked by the radiologist and conveyed to the clinician to promptly diagnose sinister pathologies such as invasive ductal carcinoma. This review focuses on these nuances and provides a step-wise algorithmic approach toward a male breast lesion, while also addressing imaging recommendations for transgender individuals.

INTRODUCTION

Lesions of the male breast are relatively uncommon. Most of these lesions are benign and present as tender, painful, palpable breast masses. Breast cancer, on the contrary, has a very low incidence in males and presents at an advanced stage as a hard, painless mass.

Red flag symptoms, such as nipple discharge, bleeding, and a fixed breast mass, which are often encountered in females, are rarely seen in male patients. Even if they occur, they are present only at a late stage. As malignant lesions are relatively uncommon in male breasts, screening mammography is not recommended in men. Ultrasound and mammography are the first-line complementary investigations performed for a male patient with suspicious breast findings[1]. Magnetic resonance imaging (MRI) may be considered as an adjunct modality in specific cases, such as evaluating the extent of disease, assessing chest wall invasion, and monitoring therapeutic response. Imaging features considered suspicious in female breasts may have different implications in male breast imaging[2].

Data in this review was reported after conducting a detailed search in PubMed and EMBASE databases from inception till June 2025. The search was conducted using the terms “male breast” AND “imaging” OR “radiology”. Data were extracted from studies describing the imaging appearances of male breast lesions, including case reports, original articles, and review articles. Studies with pure histopathological and/or surgical descriptions of male breast lesions were excluded.

This article examines the common and not-so-common lesions in male breasts and proposes a diagnostic algorithmic approach. Furthermore, the characteristic sonographic and mammographic features of male breast pathologies are described.

MALE BREAST VS FEMALE BREAST

At birth, the mammary glands are structurally identical in males and females. The breast extends from the anterior second rib superiorly to the anterior sixth rib inferiorly and from the sternum medially to the midaxillary line laterally. In neonates, mild gynecomastia is a common, transient condition resulting from the transplacental transfer of maternal estrogen before birth. In females, during the prepubertal phase, estrogen promotes ductal proliferation, branching, and growth, whereas progesterone drives stromal development and the maturation of terminal ductal–lobular units. In males, however, the surge in testosterone levels leads to ductal involution and atrophy[3,4]. Cooper’s ligaments, a core constituent of the female breast, are characteristically absent or rudimentary in men, and the pectoralis muscles are more prominent. Imaging strategies for male breast disorders differ fundamentally from those in female patients owing to anatomical, pathological, and epidemiological variations. Moreover, the male breast lacks lobular units and has a predominantly fatty composition, with sparse ductal elements, leading to a narrower spectrum of pathologies[5]. Consequently, lesions such as lobular carcinoma, fibroadenomas, phyllodes tumors, and cysts—which are frequently encountered in females—are extremely rare in males. In women, breast imaging is largely driven by routine screening programs that rely on mammography and starts from 40 years of age in the general population and earlier in high-risk individuals. In contrast, as standardized screening protocols are not available for the male breast; imaging is primarily diagnostic and symptom oriented. The American College of Radiology (ACR) recommends an age-based imaging approach in males—ultrasound in patients < 25 years of age and mammography in older individuals[6,7]. Although mammography and ultrasound remain the primary modalities, their interpretation must consider sex-specific differences. For example, microcalcifications are common and often benign in females but are rare and usually suspicious in males. Similarly, a well-circumscribed hypoechoic lesion in a woman is suggestive of a benign etiology such as fibroadenoma, whereas in men it raises a suspicion of malignancy owing to the rarity of benign solid tumors. MRI, which is widely used in females for screening of high-risk individuals and evaluation of therapeutic response, has limited and evolving applications in males due to the low incidence of disease and lack of established protocols. Therefore, male breast imaging demands heightened clinical suspicion and contextual interpretation, unlike the more algorithmic approach followed in female breast imaging. Figure 1 provides a diagrammatic representation of the male and female breast anatomy. Table 1 highlights the differences between male and female breast anatomy, disorders, and radiological approach.

Figure 1 Diagrammatic representation of male vs female breast anatomy. NAC: Nipple areola complex.

Table 1 Comparative differences in male vs female breast anatomy, imaging approach and disorders.

	Male breast	Female breast
Anatomy
Breast composition	Predominant adipose tissue with atrophic/sparse subareolar ductal elements, lacks terminal ductal lobular units	Adipose tissue with abundant ductal elements, varies with hormonal status and age
Lobular development	Absence of lobular development	Well-developed lobular anatomy
Structural supports	Minimal to no stromal architecture, absence of Cooper’s ligaments	Well-developed Cooper’s ligaments
Imaging approach	Mammography for age ≥ 25 years, Ultrasound < 25 years, or if mammography is indeterminate	Mammography screening ≥ 40 years, ultrasound adjunct for dense breast
Mammography	Smaller breast with radiolucent fatty tissue and prominent pectoralis muscle	Larger breast with variable radiographic density depending relative composition of fat and fibroglandular tissue
Sonography	Only homogeneous fat lobules	Variable sonographic echotexture depending upon relative composition of fat and fibroglandular tissue
Magnetic resonance imaging	Limited role, evaluation of chest wall involvement or disease extent, post-surgical evaluation	High risk screening, dense breast evaluation, preoperative disease extent, neoadjuvant therapy response assessment, indeterminate diagnosis
Pathologies
Benign
Most common	Gynecomastia (nodular, dendritic, diffuse). Fibroadenoma and cysts are extremely uncommon	Fibroadenoma and cysts are commonly encountered
	Well circumscribed hypoechoic mass may be malignant	Well circumscribed hypoechoic mass generally points towards benign pathology
Malignant
Histological subtypes	Invasive ductal carcinoma > papillary carcinoma. Invasive lobular carcinoma is not seen in men	Invasive ductal carcinoma > invasive lobular carcinoma, broader histological spectrum then men
Age	Diagnosed at a later age (60-70 years)	Usually 40-50 years, early age of onset in high risk females
Axillary node involvement	Higher due to advanced stage at presentation	Relatively at an advanced stage, increases with tumour size and grade
Age-adjusted survival rate[17]	Almost similar	Almost similar
Overall prognosis[17]	Worse due to delayed diagnosis	Relatively better due to screening and early stage diagnosis
Mammography	High density irregular mass with spiculated margins
	Predominantly subareolar location. Eccentric to nipple	Variable, more common in the upper outer quadrant
Microcalcifications	Uncommon	Commonly seen
Ultrasound	Irregular hypoechoic mass with spiculated margins or solid-cystic complex mass
Posterior acoustic features	Shadowing	Shadowing or enhancement
Screening	Not routinely recommended. Guidelines for high risk men[64,65]	Variable guidelines[7,19]

ROLE OF IMAGING IN DIAGNOSING MALE BREAST DISORDERS

Universal consensus on the diagnostic imaging algorithm for male breast lesions is lacking. If clinical findings indicate gynecomastia or pseudogynecomastia, no further imaging is required. Nonetheless, mammography is advised when cancer is suspected[7]. Biopsy is necessary for pathological confirmation if imaging results are inconclusive or do not rule out a benign lesion[8,9].

Mammography

Mammography is often the first-line investigation in male patients presenting with a palpable breast mass[7]. A bilateral mammogram is recommended, given the equal predisposition of both breasts to develop malignancy and the high sensitivity of the modality[10,11]. In mammography, the typical male breast presents as a uniformly radiolucent fatty tissue with a prominent radiopaque pectoralis muscle. The small size of the male breast can present challenges in obtaining accurate images. Standard mammographic views, including craniocaudal and mediolateral oblique projections, are usually sufficient for diagnosis, particularly when distinguishing the benign condition of gynecomastia from malignancy. When necessary, additional imaging techniques, such as spot compression and magnification views, can provide further clarity[11,12]. Masses are evaluated based on their shape (oval, round, or irregular), margins (circumscribed, microlobulated, obscured, indistinct, or spiculated), and density (high, equal, low, or fat-containing). Specific mammographic features for each condition have been detailed in Table 2, offering a comprehensive comparison of male breast lesions based on their mammographic margins.

Table 2 Classification of male breast lesions on the basis of mammographic abnormalities (margins).

	Well circumscribed margins	Not well circumscribed (microlobulated/indistinct/spiculated obscured)
Skin and subcutaneous tissue	Hematoma	Hematoma
	Fat necrosis	Fat necrosis
	Epidermal inclusion cyst
	Sebaceous cyst
	Hemangioma
	Venous or lymphatic malformation
Nipple areola complex and retroaerolar region	Nodular gynecomastia	Dendritic gynecomastia
	Subareolar abscess	Subareolar abscess
	Fibroadenoma	Pseudoangiomatous stromal hyperplasia
	Papilloma
Parenchyma	Papillary carcinoma	Papillary carcinoma
	Lymphoma	Invasive ductal carcinoma
	Lipoma	Invasive lobular carcinoma
Diffuse involvement/multiple masses	Lymphoma	Pseudogynecomastia
		Diffuse gynecomastia
		Mastitis
		Venous/Lymphatic malformation
		Metastases

Points needing special attention

Mammography can accurately differentiate gynecomastia from breast carcinoma[13]. Although gynecomastia is often identified by its characteristic mammographic features, it may sometimes hide malignant lesions visible on sonography. Calcifications are extremely uncommon in male breasts, and thus, even benign-appearing calcifications should be considered suspicious in male patients[5,11]. Male breast cancer is rarely associated with microcalcifications[7,8].

Sonography: Ultrasound of the male breast serves as a complementary modality in assessing patients with suspicious mammographic features. However, in young men < 25 years of age, ultrasound is often the first-line investigation[11]. Because of the small breast size, a high-frequency transducer helps clearly delineate the nature of the lesion and its extent[2]. In ultrasound, the normal male breast is primarily characterized by isoechoic fat lobules representing subcutaneous adipose tissue. Sonography-guided biopsy is often the gold standard in patients with ambiguous features[14-16]. The sonography report for male breast evaluation should adhere to ACR Breast Imaging Reporting and Data System guidelines. The report must describe the lesion’s shape (oval, round, or irregular), orientation (parallel or not parallel), margins (circumscribed, indistinct, angular, microlobulated, or spiculated), echopattern (anechoic, hyperechoic, isoechoic, hypoechoic, complex cystic-solid, or heterogeneous), and posterior features (none, enhancement, shadowing, or combined). Specific sonographic features for various conditions have been described in later sections, with Table 3 providing a comparison of lesions based on their echogenicity.

Table 3 Classification of male breast lesions on the basis of sonographic abnormalities (echogenicity).

	Hyperechoic	Hypoechoic	Complex echogenicity
Skin and subcutaneous tissue	Lipoma	Hemangioma	Fat necrosis
		Venous/Lymphatic malformation	Hematoma
		Epidermal inclusion cyst
		Sebaceous cyst
		Hematoma
Nipple areola complex and retroareolar region	Pseudoangiomatous stromal hyperplasia	Nodular gynecomastia
		Dendritic gynecomastia
		Subareolar abscess	Subareolar abscess
		Fibroadenoma	Mastitis
		Papilloma
		Pseudoangiomatous stromal hyperplasia
Parenchyma	Diffuse gynecomastia	Invasive ductal carcinoma	Papillary carcinoma
		Invasive lobular carcinoma
		Papillary carcinoma
		Lymphoma
		Metastases

Points needing special attention

As cysts are extremely uncommon in male breasts[17], cystic lesions should be considered potentially malignant and a search should be performed for mural nodules, septations, and thickened walls. A well-circumscribed hypoechoic mass should be considered suspicious, as opposed to one in a female breast[18]. Fibroadenomas are not commonly seen in male breasts. Thus, lesions with a morphology akin to fibroadenomas require further evaluation and biopsy[17].

MRI: While MRI is a well-established modality in female breast imaging with clear indications, it plays a limited but potentially valuable role in male patients[19,20]. Male breast cancer is typically well evaluated by mammography and ultrasound. However, MRI is beneficial in assessing chest wall invasion or postsurgical changes, tumor recurrence, axillary lymph node involvement, unexplained nipple discharge, implant integrity in transgender patients, and neoadjuvant therapy monitoring[21].

Points needing special attention

ACR has deemed MRI as “usually not appropriate” across all categories of male patients with symptomatic breasts[7]. Lee et al[22] in their study reported that the addition of MRI to ultrasound in the preoperative evaluation of male patients with breast cancer does not provide any survival benefit[22]. The role of MRI as a diagnostic tool, thus, needs to be explored further with respect to male breast diseases. Figure 2 provides a diagrammatic representation of various male breast lesions. The following section discusses each lesion in detail, along with specific imaging features.

Figure 2 Diagrammatic representation of various male breast lesions according to their location. 1: Epidermal inclusion cyst; 2: Sebaceous cyst with punctum; 3: Lipoma with capsule; 4: Hematoma; 5: Gynecomastia; 6: Carcinoma breast; 7: Mastitis with abscess and surrounding trabecular thickening; 8: Vascular malformation; 9: Lymphoma; 10: Axillary lymph nodes.

BENIGN LESIONS

Most lesions identified in a symptomatic male breast fall under this category. These lesions range from gynecomastia (the most common entity in male breasts) to infectious conditions, such as mastitis and benign tumors.

Non-neoplastic entities

Pseudogynecomastia: This condition often occurs in overweight or obese males. Excessive diffuse proliferation of normal fatty tissue is seen in the breast, with the absence of any glandular elements[23]. Patients may present with unilateral or bilateral breast enlargement instead of a palpable abnormality[1] (Figure 3).

Figure 3  Pseudogynecomastia: Mediolateral oblique mammography view of a 17-year-old obese male showing a diffuse bilateral increase in fat density.

Gynecomastia

Gynecomastia is the most common benign pathology in male breasts and is characterized by the proliferation of ductal and stromal elements. This condition is the routine cause of a palpable abnormality in the male breast and can be unilateral, bilateral, symmetric, or bilaterally asymmetric[24]. A bimodal age peak is seen during puberty and senescence, with patients presenting with breast enlargement, palpable concerns, or pain on one or both sides[1]. Approximately 57% of men > 44 years of age have palpable breast tissue[13]. An array of medications, anabolic steroids, cirrhosis, hyperthyroidism, and chronic kidney failure are among the usual causes of gynecomastia. On clinical examination, gynecomastia presents as a concentric, soft, easily compressible, mobile, tender mass beneath the nipple areola complex. The mammographic appearance varies depending on the stage of proliferation and maturation.

Nodular gynecomastia: This pattern represents the early florid phase of ductal and stromal proliferation and is seen in patients having gynecomastia for less than a year. Histopathologically, it is marked by periductal inflammation and surrounding edema, clinically corresponding to a painful breast. On mammography, it is seen as a fan- or triangular-shaped density in the subareolar region, which blends into the surrounding tissue without distinct borders. Ultrasound reveals a discoid or triangular hypoechoic tissue in the subareolar region[24] (Figure 4). This early phase of gynecomastia is reversible if the causative factor is eliminated.

Figure 4 Nodular gynecomastia in a 62-year-old male with tender subareolar masses in bilateral breasts. A: Mediolateral oblique; B: Craniocaudal mammography views show oval equal density masses in the retroareolar locations of both breasts (white arrows); C-E: Ultrasound images [C, D (color Doppler) and E (panoramic views)] demonstrate an oval parallel indistinct hypoechoic area (denoted by asterisks) in the retroareolar location with no evident vascularity, which is consistent with gynecomastia.

Dendritic gynecomastia: This quiescent form is characterized by a fibrotic phase, seen as stromal fibrosis and ductal dilatation on histopathological studies. On mammography, it appears as a flame-shaped retroareolar density with posterior linear projections radiating into deeper adipose tissue[1,18,25,26]. On ultrasound, dendritic gynecomastia may present as a retroareolar mass with irregular, spiculated margins and serpiginous or spider-like extensions into the surrounding tissue, features closely resembling malignancy. Nevertheless, a symmetric, flame-shaped pattern with central distribution behind the nipple is maintained, and associated architectural distortion is lacking[25]. In contrast, invasive ductal carcinoma usually presents as an eccentric, hypoechoic mass with irregular or angular margins. This condition often exhibits posterior acoustic shadowing and distortion of surrounding tissues and may be accompanied by suspicious axillary lymphadenopathy. Malignant lymph nodes typically exhibit cortical thickening, loss of fatty hilum, and rounded morphology. In contrast, benign nodes seen in gynecomastia retain an oval shape with preserved fatty hilum. This later phase is usually irreversible owing to the development of fibrosis[27] (Figure 5).

Figure 5 Dendritic gynecomastia in a 69-year-old male with a tender soft mass in the left breast. A: Mediolateral oblique mammography view showing a triangular flame-shaped area of increased density in the retroareolar location of the left breast (encircled); B: Ultrasound image showing an irregular hypoechoic retroareolar lesion with dendritic projections inside the underlying glandular fat (small white arrows).

Diffuse gynecomastia: As the name suggests, this form is characterized by an overall increase in breast density and is often seen in males with exogenous estrogen intake. Diffuse proliferation comprising both dendritic and nodular forms occurs, with an overall increase in breast density on mammogram and heterogeneity of echotexture on ultrasound[1,18,25,26]. The breast resembles a female breast on mammography and ultrasound[28] (Figure 6). Treatment includes lifestyle and medication modification, tamoxifen, androgens, and aromatase inhibitors.

Figure 6 Diffuse gynecomastia in a 42-year-old male on estrogen therapy. A: Mediolateral oblique; B: Craniocaudal mammography images showing a diffuse increase in breast density, with the male breast resembling the female breast; C and D: Ultrasound images showing diffuse deposition of glandular tissue (white arrows).

Epidermal inclusion cyst

These cysts occur frequently in men, representing the third most common benign lesion of the male breast. These develop due to hair follicle obstruction or other traumatic events, such as an insect bite or surgery. These are characteristically located beneath the skin in the periareolar region, inframammary fold, and axilla. The size varies, and the cysts appear as a round palpable mass. The glandular orifice is seen as a black dot on the patient‘s skin surface (pore sign)[29]. On mammography, they appear as a well-circumscribed mass in the subcutaneous tissue[11]. Tangential views confirm the superficial positioning of the lesion. On ultrasound, the cysts appear as well-circumscribed superficial, oval, hypoechoic masses having an “onion skin” appearance due to lamellated keratin. They contain alternating concentric hyperechoic and hypoechoic rings. In some cases, the sonographic claw sign is seen, which helps in clinching the diagnosis[13]. In addition, they often demonstrate a thin, linear, hypoechoic tract extending from the lesion to the dermis[13] (Figure 7). On color Doppler, peripheral vascularity is seen if the adjacent breast parenchyma is inflamed. Biopsy should be avoided if an epidermal inclusion cyst is suspected as it can cause rupture, potentially resulting in an inflammatory reaction in the surrounding breast tissue. Hence, these are called “touch-me-not” lesions. Antibiotics are administered for infected epidermoid cysts, whereas larger epidermoid cysts require surgical excision.

Figure 7 Epidermal inclusion cyst breast in a 23-year-old male with a palpable nodule and a history of blunt trauma to the chest. A: Magnified mediolateral oblique mammography view of the right breast showing an oval circumscribed high-density mass just below the skin (white arrow) with few foci of dystrophic eccentric calcifications (small white arrow in A). B: Ultrasound; C: Color Doppler images showing an oval circumscribed hypoechoic mass in the subcutaneous plane, with a linear hypoechoic tract reaching the skin surface (arrow in B) and no internal vascularity (C).

Hematoma and fat necrosis

These often occur as tender palpable masses in the setting of trauma to the male breast. Like hematomas anywhere else in the body, these appear as fluid collections of mixed echogenicity (ranging from hyperechoic to hypoechoic and anechoic with the progression of time) with irregular or ill-defined margins in the subcutaneous plane on ultrasound. Mammographic findings vary depending on the lesion’s stage. In the acute phase, it may present as a poorly defined mass with skin thickening and prominent trabecular patterns. However, as it progresses to the chronic stage, it becomes more clearly defined and may show fat–fluid levels. At this stage, mammography may reveal distortion, rim calcification, and well-circumscribed masses. On ultrasound, the lesion typically appears as a circumscribed, complex, heterogeneous mass that lacks vascularity and may exhibit features such as fluid–fluid levels and internal septations[1,28,30]. Hematomas and fat necrosis are routinely managed conservatively (Figure 8).

Figure 8  Fat necrosis in a 23-year-old male who suffered trauma to the right breast by football shows an irregular hyperechoic area with indistinct margins (white arrows) containing few anechoic areas.

Mastitis with an evolving abscess

Mastitis is an infection or inflammation of the breast tissue that occurs most commonly in the subareolar region of men. Ductal obstruction with a keratin plug results in inflammation and superinfection, leading to abscess formation. The causative organisms are usually bacteria such as staphylococci or, less commonly, streptococci. Patients show local signs of inflammation like pain, erythema, heat, skin thickening, and edema. On mammography, mastitis may be associated with skin and trabecular thickening along with asymmetries, which aid in the diagnosis[29]. Cases complicated by abscess formation show irregular masses with or without calcifications. Ultrasound often reveals complex fluid collections or an ill-defined subareolar mass with trabecular thickening and peripheral vascularity on color Doppler[1,31] (Figures 9 and 10). Administration of oral antibiotics and ultrasound-guided drainage are the routine therapeutic strategies[32-37].

Figure 9 Mastitis with abscess in a 61-year-old diabetic male with a tender enlarged breast. A: Ultrasound; B and C: Color Doppler images showing an irregular cystic collection with internal debris and peripheral vascularity. The surrounding fat appeared echogenic, suggesting inflammatory changes.

Figure 10  Infective collection from a 23-year-old male with a history of high-grade fever after trauma to the left breast. A: Mediolateral oblique; B: Craniocaudal mammography views showing no obvious abnormality; C: Ultrasound; D: Color Doppler images revealing a well-defined anechoic collection with peripheral internal vascularity.

Pilomatricoma

These unusual lesions arise from primitive matrix cells of the hair bulb and are rare in the male breast. Repeated skin trauma is the primary etiological factor. These lesions are also called “calcifying epitheliomas of Malherbe” and represent benign soft tissue tumors in the subcutaneous plane. On mammography, these appear as well-circumscribed calcified lesions, sometimes mimicking fibroadenomas, with dense calcifications being their hallmark. Ultrasound often reveals isoechoic to hyperechoic lesions with calcifications and distal shadowing[38]. Although the potential for malignant degeneration is slow, these are often excised for cosmetic reasons[38,39,40] (Figure 11).

Figure 11  Pilomatricoma in a 33-year-old male with a palpable left breast mass. A: Mediolateral oblique and B: Craniocaudal mammography images showing a large irregular high-density mass with circumscribed margins and coarse calcifications in the retroareolar location; C: Ultrasound; D: Color Doppler images showing an irregular lesion with extensive posterior acoustic shadowing and some internal vascularity; E and F: Histopathology images (hematoxylin and eosin, × 40) showing a circumscribed lobulated mass in subcutaneous tissue and islands of basaloid cells exhibiting abrupt keratinization without an intervening granular layer along with shadow cells and central calcification.

Venous malformation

Vascular lesions are uncommonly found in the male breast and range from hemangioma to venous and lymphatic malformations[1]. Venous malformations are the most common malformation seen in the male breast. Histologically, they are characterized by multiple, ectatic, thin-walled channels lined by flattened endothelial cells. Mammography may reveal multiple tubular densities with occasional calcifications that represent phleboliths. On ultrasound, venous malformations appear as multiple tubular cystic spaces that may show internal vascularity on color Doppler imaging[1]. Venous flow is seen on spectral Doppler interrogation, which differentiates them from lymphatic malformation that lacks flow on color Doppler. Owing to their slow internal flow, venous malformations do not have associated arteriovenous shunting (Figure 12).

Figure 12  Venolymphatic malformation. A: Mediolateral oblique mammogram with an axillary view shows multiple well-defined, lobulated densities in the axilla (arrow), some containing coarse calcifications; B: Grayscale ultrasound reveals multiple anechoic and hypoechoic compressible tubular channels in the subcutaneous plane with echogenic phleboliths (arrow), which is consistent with dilated venous and lymphatic components; C: Color Doppler ultrasound demonstrates slow flow within some of the vascular channels; D: Coronal T2-weighted fat-saturated magnetic resonance image (MRI) shows hyperintense lobulated masses (arrows) in the axilla; E: Postcontrast axial T1-weighted fat-suppressed MRI shows enhancement of the lesion (thin arrows), with nonenhancing phleboliths, which is consistent with a benign low-flow vascular malformation.

Pseudoangiomatous stromal hyperplasia

Pseudoangiomatous stromal hyperplasia (PASH) is a benign proliferative condition that may lead to the development of a solid mass[6]. PASH predominantly affects premenopausal women and rarely occurs in men, with only a few reported cases. In males, PASH is typically linked to underlying gynecomastia and hormonal imbalances, implying the role of sex hormones in its development[15]. The condition often presents as a palpable mass or as an incidental finding during imaging and resembles benign breast lesions[13,35]. Often, PASH may be encountered incidentally in breast biopsy samples. Histologically, the condition may mimic low-grade angiosarcoma or phyllodes tumor because of the presence of elongated spindle cells lining the slit-like spaces within the acellular mammary stroma. On mammography, PASH typically presents as a noncalcified, round, and well-circumscribed mass, although it may occasionally appear as a focal asymmetry. Ultrasound commonly reveals a circumscribed hypoechoic mass, with increased echogenicity or irregular margins being less frequent findings. Surgical excision can be performed in symptomatic cases, but local recurrence is common[13].

Neoplastic entities

The radiologist must be aware of the numerous benign tumors encountered in the male breast. A few of the important ones have been discussed here.

Lipoma: This encapsulated mass composed of adipocytes is the second most common benign lesion of the male breast[16,23]. Although asymptomatic, it may present as a soft or a calcified hard palpable mass[36]. On mammography, it appears as a well-circumscribed fat density mass surrounded by a capsule. The fine capsule allows visualization of the radiolucent lesion[13]. On ultrasound, it is seen as a well-circumscribed, homogeneous, isoechoic to slightly hyperechoic mass with a thin echogenic capsule in the subcutaneous plane[37,38]. Posterior acoustic shadowing is not seen (Figures 13, 14, and 15). Angiolipoma is a rare type of lipoma that contains mature fat tissue and exhibits vascular growth. Its mammographic appearance may differ based on the balance between the fatty and vascular components. On ultrasound, it often appears as an oval, circumscribed hyperechoic mass, similar to a lipoma. Surgical excision may be performed for cosmetic reasons[24].

Figure 13  Lipoma in a 34-year-old male with a palpable mass in the axilla. A: Ultrasound; B: Elastography images showing a circumscribed oval homogenous isoechoic mass (white arrow), which appeared soft on elastography.

Figure 14  Giant lipoma in a 52-year-old male with a palpable nontender mobile mass in the left breast. A: Mediolateral oblique; B: Craniocaudal mammography views showing a large, circumscribed round fat density mass in the left breast; C and D: Digital breast tomosynthesis slices demonstrating the lipoma capsule (denoted by vvv); E: Ultrasound; F: Elastography images showing a fat-containing isoechoic mass that appears soft on elastography.

Figure 15  Intrapectoral lipoma in a 45-year-old male with a palpable mass in the left breast. A: Mediolateral oblique; B: Craniocaudal mammography views showing a large, circumscribed fat density mass causing splaying of pectoralis muscle fibers in the left breast (arrows); C: Panoramic ultrasound image showing a circumscribed fat-containing echogenic mass in the intrapectoral location (arrow); D: Axial computed tomography image showing fat-containing mass splaying the pectoralis muscle (arrow); E-G: Magnetic resonance images (E: T1-weighted image; F: T2-weighted image; G: T1 fat-saturated image) demonstrating T1 and T2 hyperintense masses with suppression of fat saturation, suggestive of lipoma (arrows).

Myofibroblastoma: This uncommon benign lesion is composed of spindle cells and hyalinized collagen and is seen more commonly in elderly males than in females[38]. Myofibroblastoma presents as solitary, palpable, painless, mobile masses. On mammography, these appear as oval, equal-to-high-density noncalcified, circumscribed masses. Ultrasound often reveals a round-to-oval, circumscribed, hypoechoic mass with posterior acoustic enhancement, mimicking a fibroadenoma[13,39]. Although surgical excision is the treatment of choice, local recurrence is possible (Figure 16).

Figure 16  Myofibroblastoma in a 56-year-old male with a palpable mass in the right breast. A: Ultrasound image showing a round circumscribed heterogeneously hypoechoic mass; B: Axial; C: Sagittal noncontrast computed tomography sections demonstrating a well-defined hypoattenuating soft tissue density mass in the right breast (white arrows) with no calcifications or chest wall invasion.

Intraductal papilloma: Intraductal papilloma is a relatively uncommon benign neoplasm characterized histologically by the benign proliferation of intraductal mammary epithelium supported by a fibrovascular core[40]. Similar to papillomas in females, those in males also present with nipple discharge or a palpable retroareolar mass. Gynecomastia, anabolic steroids, and prolonged phenothiazine treatment are potential triggers for the development of intraductal papillomas in the male breast. On mammography, a circumscribed, equal-density mass is seen in the retroareolar region, often against a background of gynecomastia. Most papillomas are solitary and are located in the central breast. Ultrasound is more sensitive than mammography in picking up papillomas and reveals isoechoic-to-hypoechoic masses in the subareolar region within dilated ducts[5]. Internal vascularity may be seen within the mass on color Doppler. Often, the hypoechoic mass may not be present within a dilated duct and may be associated with a cyst. As cysts are extremely uncommon in male breasts, the presence of a cyst on ultrasound triggers the suspicion of a dilated duct distal to a papilloma[41]. Papillary carcinoma is more common than benign intraductal papilloma in men. Hence, surgical excision is recommended for a complete evaluation as aspiration or biopsy may result in histological underestimation of the pathology (Figure 17).

Figure 17  Intraductal papilloma in a 46-year-old male with a palpable abnormality. A-C: Ultrasound; D: Color Doppler images showing a circumscribed, oval, slightly hypoechoic, solid mass within a dilated duct (white arrows) with internal vascularity.

MALIGNANT LESIONS

Carcinoma of the male breast accounts for a mere 1% of new breast cancers detected and just 0.17% of all cancers in males[13]. The mean age at diagnosis is 5–10 years later than that in women, with an average age of 65 years, attributed to a low clinical suspicion and low patient awareness[17,42]. The most common symptom is a painless palpable mass; other clinical manifestations are bloody nipple discharge, nipple retraction, ulceration, or skin thickening[1]. Most of the cases present at an advanced stage, with approximately 50% exhibiting axillary nodal metastasis at initial presentation[43]. Presentation at an advanced age as well as higher stage are factors that contribute significantly to a relatively unfavorable prognosis, with poorer survival rates compared with their female counterparts[44-49]. The risk factors for the development of breast cancer in males include a positive family history, cryptorchidism, testicular injury, liver dysfunction, Klinefelter’s syndrome, a history of radiation to the chest at a young age, advanced age, and BRCA1 and BRCA2 mutations[45].

Invasive ductal carcinoma

The most common type of cancer is invasive ductal carcinoma, accounting for approximately 80% of the cases, followed by ductal carcinoma in situ, which is seen in approximately 5% of the cases[50]. Mammography is accurate in distinguishing male breast carcinoma from gynecomastia, with malignant masses having an eccentric subareolar location as opposed to the central location of gynecomastia[41,51].

Mammography often reveals an irregular, high-density, subareolar eccentric mass, with associated findings such as skin thickening, nipple retraction, or axillary lymphadenopathy[18,52,53]. Calcifications are uncommon and may be found in up to one-fourth of the cases. Calcifications, if present, are coarser in morphology, fewer in number, and more widely scattered than those in female breast cancers[13,52-54]. On ultrasound, they are seen as solid, irregular, nonparallel hypoechoic masses with microlobulated, indistinct, angular or spiculated margins[11,16]. Less commonly, they may appear as complex solid-cystic masses or may contain circumscribed margins in approximately 20% of the cases[28,50]. In addition, they may exhibit posterior acoustic shadowing or enhancement[11,28,53]. The therapeutic strategy depends on the stage of the disease, the hormone receptor status, and multidisciplinary team decisions (Figures 18 and 19).

Figure 18  Ductal carcinoma in situ in a 69-year-old male with a palpable lump in the left breast. A: Mediolateral oblique (MLO) view; B: Craniocaudal (CC) mammography view showing an irregular, high-density mass with indistinct margins in the retroareolar location with surrounding architectural distortion and nipple retraction; C and D: Contrast-enhanced mammography; C: MLO; D: CC views of recombined images showing heterogeneous postcontrast enhancement of the mass; E: Ultrasound-guided core needle biopsy image of the mass depicting the heteroechoic mass (needle denoted by vvvvv), with histopathology initially revealing ductal carcinoma in situ. Subsequent surgery, however, revealed invasive cancer.

Figure 19  Invasive breast cancer in a 74-year-old male with a hard lump in left breast. A: Mediolateral oblique (MLO) view; B: Craniocaudal (CC) view showing an irregular, high-density mass; C and D: Contrast-enhanced mammography; C: MLO and D: CC views of the recombined images showing heterogeneous enhancement; E: Ultrasound; F: Elastography images showing an irregular heteroechoic mass with microlobulated margins that appear hard on elastography; G-J: Magnetic resonance images showing an irregular mass; G: T1-weighted image showing a hypointense signal; H: T2-weighted image showing a heterogeneously hyperintense signal; I and J: DWI-ADC images showing central diffusion restriction; K: Postcontrast image showing heterogeneous septal enhancement; L: Histopathological examination image (hematoxylin–eosin, × 40) showing invasive breast cancer (no special type) composed of tumor cells arranged in clusters and tubules.

Invasive lobular carcinoma

Invasive lobular carcinoma (ILC) is extremely rare in the male breast, primarily due to the high levels of testosterone at puberty, which inhibits lobular development. A potential association with Klinefelter’s syndrome has, however, been reported due to relatively high estrogen levels and an altered androgen-to-estrogen ratio in the affected individuals[55]. Lobular development is stimulated by the high estrogen levels, exacerbating the risk of developing ILC[56]. ILC demonstrates a higher frequency of bilaterality and multicentricity as well as a propensity for gastric metastasis due to the loss of E-cadherin expression. Clinically, ILC often presents as a palpable mass or nipple change, and its diffuse growth pattern evades mammographic detection. Histopathologically, ILC is characterized by small, cohesion-lacking cells arranged in single-file patterns, often expressing estrogen and progesterone receptors but lacking HER-2 expression[57]. Mammography often shows a spiculated hypoechoic mass on ultrasound. The therapeutic approach mirrors female breast cancer protocols and involves surgery, hormone therapy, and targeted treatments with letrozole and trastuzumab based on the receptor status[58] (Figure 20).

Figure 20  Invasive lobular carcinoma in a 65-year-old male with a hard retroareolar lump. A: Mediolateral oblique; B: Craniocaudal mammography views showing an irregular high-density mass with spiculated margins, few punctate calcific foci and surrounding architectural distortion. Nipple retraction and overlying skin thickening are also observed; C: Ultrasound; D: Elastography images show an irregular mass with angular margins, which appears hard on elastography; E: Histopathology (hematoxylin and eosin, × 40); F: E-cadherin images show medium to small dyscohesive cells that lack E-cadherin expression.

Papillary carcinoma

It is the second most common invasive cancer in male breasts and occurs more often in males than in females, presenting with bloody nipple discharge[59,60]. Most male papillary carcinomas are intracystic and noninvasive. Mammography reveals a subareolar round or oval mass with spiculated or circumscribed margins. In contrast, ultrasound shows a complex cystic lesion with papillary projections along the cyst wall[53,61]. Surgical excision is the treatment of choice (Figure 21).

Figure 21  Papillary carcinoma in a 54-year-old male with a hard mass in left breast. A: Ultrasound; B: Color Doppler images showing an irregular solid-cystic mass with an eccentric solid component, with minimal peripheral vascularity.

Lymphoma

Primary lymphoma of the breast is a rare entity and is infrequently seen in both male and female breasts[16]. Secondary lymphoma, on the contrary, is relatively common. On mammography, there may be well-circumscribed to indistinct masses that lack calcifications. Sonography reveals hypoechoic solid masses with circumscribed or irregular margins, with possible hypervascularity. Biopsy is the gold standard and aids in establishing a final diagnosis. Associated axillary lymph nodes also help in arriving at the diagnosis[62]. Chemotherapy or radiotherapy is administered depending on the subtype of the tumor and extent of the disease (Figure 22).

Figure 22  Lymphoma in a 43-year-old male after 3 cycles of chemotherapy. A: Magnified mediolateral oblique view of the right breast showing a round high-density mass with partially indistinct margins and few punctate calcifications. B: Ultrasound image showing an oval hypoechoic parallel mass with circumscribed margins. C: Histopathology (hematoxylin and eosin, × 40). D: CD20 immunohistochemical staining revealed diffuse large B-cell lymphoma with sheets of atypical lymphoid cells that were positive for CD20.

Based on the role of each radiological modality and the imaging features of commonly encountered lesions, a systematic imaging approach to male breast assessment is furnished in Supplementary Figure 1.

SCREENING OF HIGH-RISK PATIENTS

Patients with a personal history of male breast cancer and a known genetic mutation are at a high risk of breast cancer, and for such individuals, the American Society of Clinical Oncology recommends annual mammography[63]. For those treated with mastectomy, mammography should be conducted on the contralateral breast, whereas bilateral mammography is advised for those who have undergone lumpectomy. In males with a history of breast cancer treated with lumpectomy but who do not have a known genetic mutation, annual screening should focus solely on the ipsilateral treated breast. The National Comprehensive Cancer Network suggests annual clinical breast examinations and training for monthly breast self-examination starting at the age of 35 for men with a known BRCA1 or BRCA2 pathogenic or likely pathogenic variant. Moreover, for men with gynecomastia and a family history of male breast cancer, annual mammography may be considered from 50 years of age or 10 years before the earliest known diagnosis of breast cancer in a male relative, whichever comes first[64-66]. As the incidence of breast cancer is low, screening of asymptomatic males is not justified, and imaging is confined only to symptomatic individuals. If symptoms and/or physical examination findings are consistent with pseudogynecomastia or gynecomastia, imaging is not recommended[7,61]. An algorithmic approach for the evaluation of a symptomatic male breast is presented in Supplementary Figure 2.

IMAGING IN TRANSGENDER MALES

The term transgender encompasses all patients whose gender identity or expression is different from the one they were born with[67,68]. Imaging in such patients is performed for several indications, including diagnostic mammography for symptomatic lesions, and as a part of presurgical and postsurgical evaluation for breast modification surgeries[69,70]. Breast cancer screening in transgender individuals should be customized based on hormone exposure, surgical status, and baseline cancer risk.

According to the 2021 ACR Appropriateness Criteria, average-risk transfeminine individuals (assigned male at birth) who have received at least 5 years of feminizing hormone therapy may be considered for screening mammography or digital breast tomosynthesis (DBT) from 40 years of age. Those with BRCA mutations, a family history of breast or ovarian cancer, prior chest irradiation, or a first-degree relative with a genetic predisposition are at a higher-than-average risk. For such individuals, screening may begin as early as 25–30 years of age, regardless of the duration of hormone therapy. In contrast, imaging is generally not recommended for average-risk transfeminine individuals with less than 5 years or no history of hormone use.

For transmasculine individuals (assigned female at birth), the presence or absence of breast tissue is the primary determinant of the screening need. Those having an average risk of < 15% and who retain native breast tissue, including patients with no chest surgery or who have undergone reduction mammoplasty, should follow standard female screening guidelines, including annual mammography from 40 years of age. Mammography or DBT is appropriate for transmasculine individuals > 30 years of age with no chest surgery or reduction mammoplasty who are at intermediate risk, such as those with atypia, lobular neoplasia, or a 15%–20% lifetime risk of breast cancer. High-risk individuals (> 20% lifetime risk) may warrant initiation at 25–30 years of age, with adjunct MRI where appropriate. Routine screening is not recommended for those who have undergone a bilateral mastectomy (“top surgery”). Gender-affirming mastectomies are often subtotal, especially in the axillary region, to preserve the chest contour, leaving behind some residual breast tissue that can still develop malignancy. Although direct data are not available for transmasculine individuals, extrapolation from high-risk cisgender women suggests that the risk of breast cancer after prophylactic mastectomy is under 2%, which is comparable to the low risk in transgender men post–top surgery. However, supporting evidence for routine breast cancer screening in this population using mammography, tomosynthesis, ultrasound, or MRI is currently lacking[71-75].

These evolving guidelines highlight the need for a risk-based, anatomy-informed, and gender-affirming approach to breast imaging in transgender populations[69,73]. In addition, breast implants, whether saline or silicone, are assessed in the same way as in natal females, with MRI being the most effective method for detecting rupture (Figure 23). Healthcare providers should be familiar with these screening protocols to ensure that transgender patients receive appropriate care[67].

Figure 23  Craniocaudal mammogram of a transfeminine (male to female) individual showing bilateral silicone implants with smooth margins and no signs of rupture.

CONCLUSION

Male breast lesions are uncommon and present unique challenges. Radiologists must be vigilant in identifying the imaging features of gynecomastia and distinguishing it from other conditions, such as breast cancer. The overlap in clinical and imaging findings between benign and malignant pathologies necessitates a comprehensive diagnostic evaluation, including mammography, ultrasound, and, when required, tissue sampling. The male breast remains an understudied and underreported topic, with limited addressal of diagnostic, therapeutic, and prognostic pathways, despite a surge in the incidence of male breast cancers. Furthermore, with the increasing awareness of transgender individuals, their unique breast cancer risks and screening guidelines must be understood. Continued education and personalized care are vital for the accurate diagnosis and management of male breast lesions, improving the outcomes across all patient populations.