Primary multifocal gastrointestinal epithelioid angiosarcoma with MYC amplification: a diagnostic pitfall mimicking poorly differentiated carcinoma: a case report

Primary gastrointestinal epithelioid angiosarcoma (EAS) is an extremely rare and aggressive malignancy. Due to its epithelioid morphology and aberrant cytokeratin expression, it frequently mimics poorly differentiated carcinoma, creating significant diagnostic challenges. Furthermore, the molecular landscape of primary EAS, particularly regarding MYC status, remains underrecognized compared to radiation-associated angiosarcomas. An 82-year-old man presented with refractory melena and severe anemia. Imaging revealed multifocal lesions involving the stomach and small intestine. The patient underwent a laparoscopic exploration and multiple segmental resections. Histologically, the tumors consisted of epithelioid cells arranged in solid sheets with extensive hemorrhage. Immunohistochemistry showed strong positivity for CD31, ERG, and CD34, accompanied by diffuse CKpan expression, mimicking carcinoma. Crucially, despite the absence of prior radiotherapy, Next-Generation Sequencing (NGS) of the gastric lesion identified significant MYC gene amplification (copy number 6.7) and a PTPRD nonsense mutation. The patient died three months after surgery. This case highlights a critical diagnostic pitfall: primary EAS can diffusely express cytokeratins. More importantly, our findings challenge the traditional view that MYC amplification is exclusive to secondary, radiation-associated angiosarcomas. We propose that MYC amplification can act as a driver in primary EAS and may serve as a biomarker for aggressive clinical behavior.