PAX8-positive, Cytokeratin-positive Intra-abdominal Ewing Sarcoma Masquerading as a Mullerian Carcinoma in a Postmenopausal Female

We report a case of an intra-abdominal Ewing sarcoma in a postmenopausal female patient whose clinical and radiological presentation closely resembled that of peritoneal carcinomatosis. Biopsy of an omental nodule revealed numerous histologic features suggestive of a Mullerian carcinoma, including gland-like rosettes, strong, diffuse PAX8 immunoreactivity and cytokeratin expression. After excluding other differential diagnostic considerations, the possibility that this might represent an intra-abdominal Ewing sarcoma was entertained. Reverse transcriptase polymerase chain reaction testing demonstrated the presence of an EWSR1-ERG fusion transcript, confirming the diagnosis. The differential diagnostic considerations when dealing with this unusual clinical scenario and the uncommon yet important pitfall of PAX8 immunoreactivity in Ewing sarcoma are discussed.
Source: International Journal of Gynecological Pathology - Category: Pathology Tags: PATHOLOGY OF THE UPPER TRACT: Case Reports Source Type: research