Hydrocele and Unexpected Diagnosis: Malignant Mesothelioma of Tunica Vaginalis Testis

Testicular mesothelioma originating from tunica vaginalis is a very rare disease. A 70-year-old man complained of left testicular swelling and was operated with the clinical diagnosis of hydrocele. Intra-operative examination revealed diffuse thickening of tunica vaginalis, which was thought to be inflammatory and benign by the urologist. Nevertheless an incisional biopsy was performed and atypical mesothelial proliferation was reported in histopathology. Morphologic findings were insufficient for definitive diagnosis of malignancy. Patient was followed-up for ten months. Due to the persistance of paratesticular thickening and additional appearance of nodularities, left inguinal orchiectomy was performed. Microscopy revealed classical malignant mesothelioma originating from tunica vaginalis. Two years after the diagnosis, patient had metastases to the paraaortic lymph nodes. Malignant mesothelioma of the testis may represent with diagnostic difficulties both clinically and pathologically. In all cases where paratesticular tissues may deviate from normal, mesothelioma must enter into the differential diagnosis. J Med Cases. 2011;2(6):275-278 doi: https://doi.org/10.4021/jmc396w