Malignant Desmoplastic Type Mesothelioma Mimicking a Fibrous Pseudo- tumor of the Tunica Vaginalis: A Case Report and Literature Review

Malignant mesothelioma is an uncommon tumor of serosal surfaces. The most common sites of origin include the pleura and the peritoneum. Malignant mesothelioma of the tunica vaginalis testis is rare. We describe a 78 year-old man with a 2-month history of a rapidly enlarging scrotum. The initial pathologic diagnosis was fibrous pseudotumor by the presence of cellular spindle cells and the background of dense fibrous tissue. However, further immunohistochemistry revealed characteristic features of desmoplastic variant mesothelioma. Mesothelioma of the peritoneum and tunica vaginalis tends to be the epithelioid type. The purely desmoplastic-type mesothelioma of the tunica vaginalis has never been reported. Immunohistochemistry is essential to the diagnosis.