Primary small intestinal epithelioid angiosarcoma: a potential diagnostic pitfall due to abnormal expression of cytokeratin

Background: Primary small intestinal epithelioid angiosarcoma (EAS) is a very rare tumor, which originates from endothelial cell with high mortality. Only 66 cases of small intestinal angiosarcoma including primary or metastatic were reported in the current literature. Histologically, hemangiosarcoma with epithelioid cell morphology is more rare, so we report a case of EAS which is easily misdiagnosed as poorly differentiated carcinoma. We also reviewed the literature about small intestinal angiosarcoma. Case presentation: The patient was a 60-year-old man, who initially presented black stool with no obvious inducement for 7 days, gradually feeling dizzy and fatigue for 3 days. Abdominal CT showed that the intestinal wall of the upper jejunum was thickened near the duodenum. After enhancement, the intestinal wall could be enhanced evenly. With the time going on, the contrast media could be concentrated gradually, and the active hemorrhage was considered. Enteroscopy revealed a 30 mm × 20 mm red polypoid mass in the jejunum. A biopsy of polypoid mass exhibited malignant tumor, histopathology considered poorly differentiated cancer. The patient subsequently underwent resection of the jejunal neoplasm. Immunohistochemistry vascular markers and cytokeratin were postive，but C-MYC protein was negative, and showed no amplification of C-MYC gene by Fluorescence in situ hybridization （FISH）. The histopathology with immunohistochemical and FISH studies confirmed the diagnosis of primary small intestinal EAS. 24 months after surgery, the patient had no evidence of recurrence and metastasis. Conclusion: Primary small intestinal EAS is a rare malignancy of endothelial origin with uncertain etiology and often has a poor prognosis.The abnormal cytokeratin expression in epithelioid angiosarcomas represents a potential diagnostic pitfall for pathologists. FISH detection of C-MYC gene amplification may have some value in the diagnosis of primary or metastatic small intestinal AS.An accurate pathological diagnosis relies on histopathology with immunohistochemical stains of endothelial markers. Surgical resection remains the best treatment option for small intestinal angiosarcoma.