Gastrointestinal stromal tumor colliding with angiosarcoma.

The collision of gastric tumors is rare, and those involving gastrointestinal stromal tumor and angiosarcoma have not been previously reported. This article reports a gastric tumor involving collision of gastrointestinal stromal tumor and angiosarcoma. The patient was an 81-year-old man who presented with dyspepsia and large gastric mass. The mass showed a proliferation of spindle cells expanding the muscularis propria. Most of the tumor consisted of spindle cells with low-grade cytology that were positive for CD117 (c-kit), indicating gastrointestinal stromal tumor. Occasional prominent foci showed dissecting and anastomosing channels of ectatic vascular spaces lined by cytologically malignant cells that were positive focally for CD117 and diffusely positive for multiple vascular markers, indicating angiosarcoma.