Primary peritoneal carcinoma: a rare neoplasm with pleomorphic trophoblastic morphology

We report a case of primary peritoneal carcinoma with trophoblastic morphology in a 78‐year‐old woman, diagnosed by histological and immunohistochemical analysis of surgically resected specimens, including the omentum and part of the small bowel. Microscopically, the resected specimens showed diffuse infiltration of a poorly differentiated tumor. Numerous large, often multinucleated cells were seen, and mitotic figures were frequent. Immunohistochemical staining showed a positive reaction for most cytokeratins, EP4, EMA, CA‐125, Glut1, WT1, β‐hCG and PLAP. We reached a diagnosis of primary peritoneal carcinoma with trophoblastic morphology. To our knowledge this morphology of a primary peritoneal carcinoma has not been described previously.