The diagnostic utility of PAX8 immunostaining of malignant peritoneal mesothelioma presenting as serous ovarian carcinoma: A single-center report of two cases.

Malignant peritoneal mesotheliomas (MPMs) are rare and progressive tumors, which may present similarly to primary peritoneal carcinoma or ovarian carcinoma (OC). The current study reports two cases of MPM that initially presented with the features of OC, for which paired box 8 (PAX8) immunostaining was found to be useful for diagnosis. The two patients were women, aged 58 and 56 years, respectively. The primary presenting symptoms and clinical findings included prolonged abdominal pain, abdominal swelling and cough. The two cases were initially diagnosed as OC and were treated with primary debulking surgery. The patient in case 1 had no history of asbestos exposure, while the patient in case 2 did. Final diagnoses were determined based on histological and immunohistochemical results, which included negative PAX8 immunostaining, and which were consistent with MPM. The present cases demonstrated that PAX8 negativity may be a useful diagnostic biomarker for differentiating MPM from OC.