Chronic expanding hematoma is a hematoma that gradually increases in size over a period. Only a few studies reported a chronic expanding hematoma that turned into a malignancy, we report a rare presentation of a chronically expanding hematoma that after 10 years became an angiosarcoma. This is a 41-year-old gentleman, presented to our Emergency Department, complaining of left upper gluteal pain and bleeding after he underwent hematoma evacuation in a private hospital. The patient was then admitted for infected hematoma evacuation. The patient tolerated the surgery
however, there was a persistent drop of hemoglobin postoperatively. All pathology and culture results were inconclusive. We then proceeded with computer tomography angiogram, which came back negative. Magnetic resonance imaging was then requested, which came with a slight interval change and a suspicious area, and so interventional radiology was involved to take a biopsy, which came back as angiosarcoma and then the patient underwent wide local excision with reconstruction.