Radiation-Induced Epithelioid Angiosarcoma of the Urinary Bladder Mimicking Sarcomatoid Carcinoma: A Rare Entity and Literature Review.

Epithelioid angiosarcoma of the bladder is an exceptionally rare and aggressive vascular malignancy, characterized by a poor prognosis due to its high propensity for invasion and metastasis. Due to its rarity, the diagnosis is often challenging and may be misinterpreted as other high-grade malignancies. Patients commonly present with advanced-stage disease, including muscle invasion at the time of diagnosis, leading to unfavorable clinical outcomes. We report a 73-year-old male patient with a history of metastatic colon cancer (to the cervical lymph node) who presented with gross hematuria. Imaging and cystoscopy evaluation revealed a mobile bladder mass with possible right anterior bladder wall thickening and necrotic tissue. Transurethral resection of the bladder tumor performed outside was initially interpreted as muscle-invasive poorly differentiated carcinoma with sarcomatoid differentiation. Upon reviewing the slides at our institution, the diagnosis was revised to epithelioid angiosarcoma of the bladder. Despite an aggressive multimodal therapeutic approach, including chemotherapy and radical prostatectomy, the patient's clinical condition progressively worsened, ultimately leading to mortality 11 months post-diagnosis. This case report highlights the diagnostic challenges and aggressive nature of epithelioid angiosarcoma of the bladder, emphasizing the need for early detection and exploration of novel therapeutic strategies to improve patient outcomes.