Splenic hamartoma mimicking angiosarcoma: A case report

Abstract

BACKGROUND

Primary splenic lesions are rare and often detected incidentally through imaging, biopsy, or autopsy, typically without distinct clinical symptoms. Although imaging can help differentiate benign from malignant lesions, splenic hamartomas, and angiosarcomas may exhibit overlapping features, making diagnosis challenging. This report presents a case of splenic hamartoma suspected to be an angiosarcoma based on preoperative imaging. Splenic hamartomas that mimic angiosarcomas are exceedingly rare.

CASE SUMMARY

A 33-year-old male presented to the Department of Emergency with frank red blood hematemesis and a 1-week history of epigastric pain. On arrival, he was alert and hemodynamically stable. Contrast-enhanced abdominal computed tomography revealed splenomegaly with significant engorgement of the portal and splenic veins, along with a diffuse nodular splenic lesion measuring 8.2 cm × 6.2 cm. Following esophageal varix ligation, abdominal magnetic resonance imaging demonstrated iso- to high-signal intensity within the splenic mass and multiple hypervascular lesions in the right hepatic lobe, raising suspicion for splenic angiosarcoma with hepatic metastases. ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography showed diffusely mild increased metabolic activity in the spleen. The patient subsequently underwent splenectomy and liver biopsy. Histopathological examination revealed chronic inflammation in the liver, and the splenic lesion was confirmed to be a splenic hamartoma. The patient successfully returned to work and remains in good health.

CONCLUSION

This rare case of splenic hamartoma mimicking angiosarcoma highlights the importance of differential diagnosis in managing splenic tumors.

Key Words: Hamartoma; Angiosarcoma; Spleen; Preoperative imaging; Case report

Core Tip: Splenic hamartomas are rare benign lesions that can closely mimic malignant tumors such as splenic angiosarcomas on imaging. We present a case initially suspected as splenic angiosarcoma with hepatic metastases, but histopathology after splenectomy confirmed splenic hamartoma. This rare case of splenic hamartoma mimicking angiosarcoma highlights the importance of differential diagnosis in managing splenic tumors.

INTRODUCTION

Splenic angiosarcoma is an exceptionally rare and aggressive malignancy originating from the endothelial cells of blood vessels in the spleen[1]. The annual incidence rate of primary splenic angiosarcoma is estimated to be between 0.14 and 0.25 cases per million individuals, with a peak incidence in patients aged 50-60 years. Its exact pathogenesis remains unknown, and unlike hepatic angiosarcomas, no established association exists between environmental and occupational exposure to carcinogens[2]. Considering its non-specific clinical presentation, imaging studies play a critical role in the initial evaluation. However, a definitive diagnosis is typically made through histopathological examination. In contrast, splenic hamartomas are hypervascular lesions composed of normal splenic white and red pulps. Cases of splenic hamartomas have been widely reported in the literature[3]. Typically asymptomatic, they are often discovered incidentally through imaging, biopsy, or autopsy. The reported incidence ranges from 0.024% to 0.13%, with 20% of cases occurring in children[4,5]. Although splenic hamartoma is a rare benign disease, some cases exhibit suspicious features, making its differentiation from malignant lesions challenging because of the absence of distinct symptoms or signs. Splenic biopsy is often restricted because of the risk of rupture and potential dissemination of cancer cells. Therefore, preoperative imaging is instrumental in diagnosis. In this report, we present the case of a 33-year-old male with splenic hamartoma that radiologically mimicked angiosarcoma preoperatively. To the best of our knowledge, this is an exceptionally rare case of splenic hamartoma that closely resembles an angiosarcoma.

CASE PRESENTATION

Chief complaints

A 33-year-old male presented to the Department of Emergency with frank red blood hematemesis on the day of admission and a one-week history of epigastric pain and nausea.

History of present illness

The patient had no history of present illness.

History of past illness

The patient was diagnosed with a giant cell tumor in the left wrist and underwent seven operations. The patient had no other significant medical history.

Personal and family history

The patient reported no relevant medical or family history.

Physical examination

The patient experienced a single episode of hematemesis, estimated to be approximately half a paper cup of bright red blood. Upon presentation, he appeared pale and reported persistent abdominal discomfort and nausea. Physical examination of the chest and abdomen revealed no remarkable findings. At the time of arrival to the Department of Emergency, the patient was alert and oriented, with stable vital signs: Blood pressure, 120/80 mmHg; heart rate, 98 beats per minute; respiratory rate, 16 breaths per minute; body temperature, 36.3 °C; and oxygen saturation, 98% on room air.

Laboratory examinations

Biochemistry values upon admission as shown in Table 1. Arterial blood gas analysis and other laboratory tests performed at the time of admission revealed no abnormalities.

Table 1 Biochemistry values upon admission.

	Value	Unit	Reference range	Result
White blood cell count	6.99	109/μL	3.8-11.0	Normal
Neutrophil count	85.7	109/μL	1.5-7.0	Elevated
Hemoglobin	6.9	g/dL	13.5-17.5	Low
Hematocrit	23.1	%	39.0-53.0	Low
Platelet count	157	109/μL	140-420	Normal
AST	26	U/L	0-40	Normal
ALT	45	U/L	0-40	Slightly elevated
ALP	103	U/L	40-129	Normal
BUN	16.6	mg/dL	6-26	Normal
Creatinine	0.89	mg/dL	0.4-1.2	Normal
INR	1.24		0.88-1.12	Slightly elevated
C-reactive protein	0.05	mg/dL	0-0.5	Normal
CEA	0.8	ng/mL	0-5.0	Normal
CA 19-9	4.85	U/mL	0-39	Normal

AST: Aspartate aminotransferase; ALT: Alanine aminotransferase; ALP: Alkaline phosphatase; BUN: Blood urea nitrogen; INR: International normalized ratio; CEA: Carcinoembryonic antigen; CA: Carbohydrate antigen.

Imaging examinations

Contrast-enhanced abdominal computed tomography (CT) revealed approximately 8.2 cm × 6.2 cm sized diffuse nodular lesion in the spleen, containing a peripheral enhancing mass-like lesion (Figure 1A), indicative of splenic angiosarcoma. Necrosis was observed at the center of the splenic mass (Figure 1B). Multiple indeterminate lymph nodes were identified in the small bowel mesentery. Abdominal magnetic resonance imaging (MRI) revealed hemosiderosis in the central portion of the splenic mass, exhibiting low signal intensity on both T1-weighted imaging (T1WI) and T2WI (Figure 2A and B). On dynamic contrast-enhanced MRI, the splenic mass displayed iso-to-high signal intensity (Figure 2C and D). Additionally, contrast-enhanced MRI revealed multiple hypervascular masses in the right hepatic lobe (Figure 2E). Consequently, splenic angiosarcoma with hepatic metastasis was suspected. ¹⁸F-fluorodeoxyglucose positron emission tomography-CT demonstrated splenomegaly with mildly and diffusely increased metabolic activity, raising suspicion of hematologic malignancy (Figure 2F).

Figure 1 Abdominal contrast-enhanced computed tomography images with postoperative course in a 33-year-old man. A: Arterial phase contrast-enhanced computed tomography (CT) shows an 8.2 cm × 6.2 cm mass lesion with peripheral rim enhancement (arrowheads); B: Portal venous phase CT reveals a centrally necrotic lesion (orange arrow) with engorged splenic vein (arrowheads); C: On postoperative day 5, portal venous phase CT demonstrates massive splenic vein thrombosis (arrowheads) and a resection site hematoma (orange arrow); D: postoperative day 5, portal venous phase CT also reveals significant intrahepatic and extrahepatic portal vein thrombosis (arrowheads); E: At the 3-month postoperative follow-up, portal venous phase CT shows a remarkable reduction in portal vein thrombosis (arrowheads); F: Significant resolution of remnant splenic vessel thrombosis (arrowheads) and resection site hematoma is observed (orange arrows); G: At the 1-year postoperative follow-up, portal venous phase CT confirms substantial resolution of resection site hematoma (arrowheads); H: Complete resolution of extrahepatic and intrahepatic portal vein thrombosis is seen (orange arrow), with no evidence of recurrence or other abnormalities.

Figure 2 Gadoxetic acid-enhanced liver magnetic resonance imaging and ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography examination. The central portion of 8.2 cm × 6.2 cm splenic mass contained hemosiderosis (orange arrow) showing low signal intensity. In dynamic contrast enhanced magnetic resonance images, the splenic mass showed iso to high signal intensity. Contrast enhanced magnetic resonance images demonstrated the multiple hypervascular masses (arrowheads) in liver right hepatic lobe. Positron emission tomography-computed tomography demonstrated splenomegaly with mildly diffusely increased metabolic activity, raising suspicion of hematologic malignancy. A: T1-weighted image; B: T2-weighted image; C-E: In dynamic contrast enhanced magnetic resonance images; F: Positron emission tomography-computed tomography examination image.

Pathological and histological findings

Endoscopic variceal ligation was performed preoperatively to evaluate and manage the esophageal varices that caused hematemesis. Hemostasis was achieved at six points. To identify malignancy, the patient underwent exploratory laparotomy with splenectomy and liver biopsy. A frozen liver biopsy performed at segments 2 and 4a revealed chronic inflammation, and no additional resection was deemed necessary. The resected spleen weighed 1205.8 g and measured 21.7 cm × 15.5 cm × 6.3 cm, with an intact capsule and no signs of congestion (Figure 3A). Gross examination revealed an ill-defined yellow-white solid mass with hemorrhage, measuring 4.5 cm × 2.5 cm × 2 cm (Figure 3B). The lesion size observed on CT was found to include a pseudo-lesion, as confirmed by the pathological findings. Immunohistopathological examination revealed CD8+ sinusoidal staining (Figure 3C) positive for CD34, smooth muscle actin, E-twenty-six-related gene, and CD68. The lesions were weakly positive for pan-cytokeratin antibody and negative for desmin, S100 protein, epithelial membrane antigen, CD21, and leukocyte common antigen. Microscopically, vascular proliferation composed of disorganized red pulp elements and hemorrhage were observed (Figure 3D), consistent with the diagnosis of splenic hamartoma.

Figure 3 Surgical specimen with histopathological analysis and immunohistochemical examination after splenectomy. A: The surgical specimen measured 21.7 cm × 15.5 cm × 6.3 cm, with an intact capsule and no signs of congestion; B: Gross examination reveals an ill-defined yellow-white solid mass with hemorrhage, measuring 4.5 cm × 2.5 cm × 2 cm; C: Immunohistochemical staining for CD8+ sinuses (× 200); D: Microscopic findings show vascular proliferation composed of disorganized red pulp elements (left from red line) and hemorrhage (right from red line), visualized with hematoxylin-eosin staining (× 100).

FINAL DIAGNOSIS

Based on the histopathology results, the final diagnosis of splenic hamartoma was confirmed.

TREATMENT

The patient experienced acute upper gastrointestinal bleeding due to prominent splenic and gastroesophageal varices, which were attributed to idiopathic portal flow reduction. Ceftriaxone and metronidazole were administered for antimicrobial prophylaxis. Considering the reduced risk of postoperative infection, antibiotics were discontinued on postoperative day 5 (POD5)[6]. Following splenectomy with liver biopsy, a follow-up POD5 CT scan revealed a hematoma at the resection site and massive thrombosis in the splenic, extrahepatic, and left portal veins (Figure 1C and D). Consequently, warfarin therapy was initiated and adjusted to maintain a prothrombin time-international normalized ratio within the target range of 2.0-3.0. After three months, CT imaging demonstrated significant improvement, prompting a transition from warfarin to apixaban. The patient was prescribed apixaban 5 mg twice daily for 6 months, followed by a dose reduction to 2.5 mg twice daily for an additional 6 months, after which anticoagulation therapy was discontinued[7].

OUTCOME AND FOLLOW-UP

The patient was discharged on POD15. A 3-month follow-up CT performed on an outpatient basis showed substantial improvement in thrombosis (Figure 1E and F). Subsequently, CT scans were conducted at 6-month intervals, and the patient continued to show good progress without any issues requiring readmission. At the 1-year postoperative follow-up, portal venous phase CT confirmed substantial resolution of the resection site hematoma. Complete resolution of the extrahepatic and intrahepatic portal vein thrombosis was observed, with no evidence of recurrence or other abnormalities (Figure 1G and H). Three months postoperatively, the patient secured employment and has since been leading a normal life.

DISCUSSION

A splenic hamartoma is a benign tumor composed of an overgrowth of mature splenic tissue. The reported incidence is approximately three cases per 200000 splenectomies, making it a very rare condition. It is more common in women, with 20% of cases diagnosed among children[5]. Most patients are asymptomatic; however, 15% experience symptoms related to hypersplenism such as abdominal pain and cytopenia[4,5]. Fever and malaise are observed more frequently in children. Splenic hamartomas are often incidentally detected during imaging studies. Recent advancements in imaging techniques have made preoperative diagnosis possible. However, owing to the non-specific nature of clinical manifestations, accurate diagnosis remains challenging. A definitive diagnosis requires histopathological examination, which often requires splenectomy. However, splenectomy carries risks, such as increased thrombotic events and infections. Therefore, distinguishing splenic hamartomas from other splenic lesions using imaging modalities is crucial. On imaging studies, such as ultrasonography, CT, and MRI, both splenic hamartomas and angiosarcomas can appear as well-defined masses. Hamartomas typically present as hypoechoic solid masses with hypervascularity on color Doppler ultrasonography and post-contrast enhancement. However, angiosarcomas may also appear as heterogeneous masses with areas of necrosis or hemorrhage, complicating differentiation based solely on imaging[8]. Wang et al[9] described the imaging characteristics of splenic hamartomas. On ultrasonography, hamartomas appear as hyperechoic solid masses compared to the normal splenic parenchyma, with increased blood flow on color Doppler due to hypervascularity. On CT scans, they appear as isodense or hypodense solid masses relative to the adjacent splenic tissue. MRI findings showed isointensity on T1WI and heterogeneous hyperintensity on T2WI. Immunohistochemistry plays a crucial role in differentiating splenic hamartomas from angiosarcomas. Histologically, splenic hamartomas exhibit irregular vascular channels lined with plump endothelial cells. Immunohistochemical markers typically positive for splenic hamartomas include CD8, CD31, CD34, factor VIII-related antigens, and vimentin. Differential diagnoses include other vascular and solid mass-forming lesions, such as hemangioma, lymphangioma, hemangioendothelioma, sclerosing angiomatoid nodular transformation, and angiosarcoma[10]. A study has reported an association between splenic hamartomas and hematological or solid malignancies, including squamous cell carcinoma, renal cell carcinoma, and thymoma[11]. Additionally, splenic hamartoma has been observed in hamartoma-associated syndromes such as tuberous sclerosis and Wiskott-Aldrich-like syndrome[12,13]. Notably, one-third of splenic hamartomas are associated with accessory spleens[13]. In cases where splenic hamartomas are associated with hematological disorders, splenectomy may be considered. In addition, when malignant lesions cannot be eliminated based on imaging findings alone, diagnostic splenectomy may be necessary. Several studies have documented cases of splenectomy for suspected malignancies. Hsu et al[14] reported a case in which a hypervascular splenic tumor was suspected to be an angiosarcoma with multiple liver metastases. The patient underwent an exploratory laparotomy, splenectomy, and liver biopsy. Frozen section analysis suggested benign features, and the final pathological diagnosis confirmed splenic inflammatory pseudotumor. Akkucuk et al[15] reported a case of splenic hematoma in a patient with a history of a car accident 18 months prior to presentation. Ultrasonography and MRI failed to differentiate it from malignancies such as angiosarcoma. Histopathological findings confirmed an organized hematoma. Accurate differentiation between splenic hamartomas and angiosarcomas is vital because of the significant differences in treatment and prognosis. Although hamartomas are benign and may not require intervention unless symptomatic, angiosarcomas are highly aggressive malignancies that require prompt surgical treatment and often have a poor prognosis. Therefore, when imaging and clinical findings are inconclusive, a definitive diagnosis based on histopathological examination, often following splenectomy, is essential. In our case, the preoperative diagnosis was particularly challenging due to overlapping clinical and radiologic features of splenic hamartoma and angiosarcoma. Both conditions can be asymptomatic. Hamartomas may cause abdominal pain due to hypersplenism, whereas angiosarcomas may present with nonspecific symptoms such as vague abdominal discomfort[14,15]. These similarities limit the diagnostic value of clinical presentation alone. Imaging findings also contributed to the difficulty. The lesion in our patient showed a heterogeneous mass with necrosis and hemorrhage on MRI and had irregular margins, features commonly associated with malignant tumors. Both hamartomas and angiosarcomas can appear hypervascular, and angiosarcomas may mimic benign enhancement patterns. As a result, imaging alone was insufficient for a definitive diagnosis. In such cases with ambiguous findings, splenectomy serves as an essential diagnostic and therapeutic approach. In our patient, preoperative imaging raised suspicion for splenic angiosarcoma with possible liver metastases, prompting splenectomy. However, final histopathological examination confirmed the lesion to be a splenic hamartoma. Cases of splenic hamartoma mimicking angiosarcoma are rare. Therefore, reporting such cases is important for improving diagnostic accuracy and guiding clinical decision-making in similarly complex presentations.

CONCLUSION

Splenic lesions are difficult to diagnose based solely on imaging, and biopsies are often limited due to the risk of rupture and potential dissemination of cancer cells. This rare case of splenic hamartoma mimicking angiosarcoma underscores the importance of differential diagnosis and expands the clinical perspective of physicians managing splenic tumors.