Abstract
Angiosarcomas are rare and aggressive malignant neoplasms of vascular or lymphatic endothelial origin, accounting for approximately 2% of soft-tissue sarcomas. They occur predominantly in the skin and superficial soft tissues, particularly in the head and neck region and the breast, whereas gastrointestinal involvement is exceptionally rare. Previous radiotherapy is a well-established risk factor for secondary angiosarcoma. However, radiation-associated gastrointestinal angiosarcomas are extremely uncommon and have been reported predominantly in the small bowel. We report the case of a 55-year-old woman who presented with abdominal pain, hemorrhagic ascites, intermittent rectal bleeding, severe anemia, anorexia, and weight loss 16 years after pelvic radiotherapy and cisplatin-based chemotherapy for cervical squamous cell carcinoma. Computed tomography revealed circumferential thickening of the cecum and right colon with abundant hyperdense ascites. Colonoscopy showed an obstructing, ulcerated, and contact-bleeding mass involving the cecum and right colon. Histopathological examination of endoscopic biopsies revealed a poorly differentiated malignant vascular neoplasm. Immunohistochemical staining was positive for cluster of differentiation (CD)31 and CD34 and negative for cytokeratin, CD3, CD20, and Human Herpesvirus (HHV)8, with a Ki-67 proliferation index of 40%, supporting the diagnosis of colonic angiosarcoma. Surgical resection was considered; however, the patient developed a massive bilateral pulmonary embolism and died seven days after admission. Given the prolonged latency and the histological distinction from the primary cervical carcinoma, a possible radiation-associated etiology was considered. Nevertheless, the original radiotherapy plan was unavailable, preventing definitive confirmation that the tumor arose within the irradiated field. This case highlights the diagnostic difficulty, aggressive clinical course, and poor prognosis of colonic angiosarcoma following pelvic radiotherapy.