A compendium of male breast imaging: The road less traveled

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]

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

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