Angiosarcoma is a rare and aggressive vascular malignancy. Primary renal angiosarcoma accounts for only ~1% of all angiosarcomas, making it an extremely uncommon renal malignancy. Due to its rarity and nonspecific symptoms, it is frequently misdiagnosed as other renal tumors. We present a case of primary renal angiosarcoma in a 74-year-old man.

A 74-year-old man with a history of hypertension and urolithiasis presented with a 2-week history of gross hematuria and left flank pain. He also reported abdominal pain and bloody stools. Laboratory tests revealed mild anemia and impaired renal function. Urinalysis showed significant hematuria. Abdominal CT scan identified a 6.2 × 5.8 × 4.2 cm lesion in the upper pole of the left kidney with peripheral enhancement and invasion into the descending colon. The patient underwent laparoscopic left nephroureterectomy with retroperitoneal lymph node dissection and laparoscopic hemicolectomy. Histological examination showed hemangioma-like anastomosing vascular channels lined by atypical endothelial cells with necrosis. Immunohistochemistry revealed diffuse positivity for ERG, CD31, and CD34, and negativity for PAX8 and cytokeratin, confirming the diagnosis of angiosarcoma. The postoperative course was uneventful, and the patient was discharged in stable condition.

Angiosarcoma comprises <2% of all soft tissue sarcomas and <1% of adult solid tumors. Primary renal involvement is exceptionally rare. Common symptoms include flank pain, hematuria and palpable mass, all of which mimic more prevalent renal neoplasms. Imaging studies may assist in identifying renal masses but lack specificity for angiosarcoma. Definitive diagnosis requires histopathological confirmation and immunohistochemical staining, with CD31 and CD34 being key markers. Due to its rarity, no standardized treatment guidelines exist. Surgical resection remains the mainstay of therapy when feasible. The roles of chemotherapy and radiation remain unclear and are generally considered on a case-by-case basis. Prognosis is poor, with most cases presenting with metastatic disease at diagnosis. Tumor size and the presence of metastasis at presentation are known prognostic indicators.

Renal angiosarcoma is a rare but highly aggressive neoplasm with a dismal prognosis. Diagnosis requires tissue confirmation due to its nonspecific clinical and radiologic features. Further research is essential to establish evidence-based management strategies for this challenging malignancy.