Malignant peritoneal mesothelioma, clear cell variant, in a female and its differentiation from clear cell carcinoma

Epithelial type malignant mesothelioma with a clear cell morphology is rare, and no case arising in the peritoneum of a female patient has been reported. Here we report a case of clear cell mesothelioma that developed in the peritoneum of a 61-year-old female. The patient died from massive ascites and respiratory failure 11days after her hospital admission. The autopsy demonstrated marked thickening of the omentum and a yellowish-whitish tumor diffusely covering the abdominal organs. The predominantly solid tumor was characterized microscopically by the growth of atypical cells with an abundant clear cytoplasm. The immunohistochemical study suggested mesothelioma rather than carcinoma. Electron microscopy showed the long and slender villi of the tumor cells, confirming the diagnosis. Primary clear cell carcinoma of the peritoneum, like clear cell mesothelioma, is rare and was also a diagnostic consideration in this patient. The differentiation between these two tumors is discussed herein.