Primary peritoneal clear cell carcinoma versus ovarian carcinoma versus malignant transformation of endometriosis: a vexing issue.

Peritoneum is a site for both primary and secondary tumors. Primary peritoneal tumors are fairly rare. The most common primary tumors of the peritoneum are malignant mesothelioma and serous papillary adenocarcinoma. Clear cell carcinoma of the peritoneum is extremely rare and often misdiagnosed as mesothelioma, serous carcinoma, or metastatic adenocarcinoma, so it represents a diagnostic challenge for both clinicians and pathologists. Up to date, to the best of our knowledge, only 11 cases of primary peritoneal clear cell carcinoma have been reported in the English literature. Distinguishing this tumor of the peritoneum versus ovarian carcinoma can be problematic. Herein, we report a rare case of primary peritoneal clear cell carcinoma occurring in a 49-year-old woman, along with a review of the literature.