Multifocal Malignant Epithelioid Mesothelioma of the Testis

Abstract

Abstract Introduction/Objective Testicular mesothelioma is an extremely uncommon entity, and presents with non-specific clinical symptomatology, including painless scrotal enlargement and hydrocele formation. Testicular mesothelioma arising from the mesothelial cells of the tunica vaginalis accounts for 0.3%-5% of all mesothelioma cases and is often associated with poor prognosis. While the pathophysiology of this entity remains unclear, exposure to asbestos and long-standing hydrocele are associated risk factors. Methods/Case Report Herein, we present a case of a 65-year-old male with history of hypertension, 4-year history of left scrotal hydrocele, and a 7-month history of painless, progressively enlarging left scrotum. Scrotal ultrasound revealed a left, septated hydrocele with multiple heterogenous intratesticular masses. A left radical orchiectomy was performed and the specimen was sent to pathology for histopathological evaluation. Gross examination revealed a tan-brown fluid-filled cystic and solid mass measuring 7.5 x 4.0 x 3.5 cm involving the entire epididymis with multiple pink-tan, friable, papillary excrescences and nodules in the intratesticular parenchyma. Microscopic examination revealed a cystic and solid lesion with tubular and papillary architecture comprised of cuboidal cells with cellular pleomorphism, irregular nuclear contour, and dense chromatin involving the epididymis, rete testis, tunica albuginea, the testicular parenchyma including the hilar fat and the spermatic cord stroma. Immunohistochemical staining of the lesion demonstrated positive staining with AE1/AE3, CK7, WT1, PAX8, Calretinin, Vimentin, Podoplanin D2-40, and lack of staining with Chromogranin, Inhibin, MART-1, SMA, AFP, CD99, S100, c-kit, PLAP, HCG, MOC31, BerEP4. Based on the histomorphology and the immunophenotype of the lesion, a diagnosis of an epithelioid-type malignant mesothelioma was favored. Results (if a Case Study enter NA) N/A. Conclusion Malignant epithelioid mesothelioma of the testis is a rare and important clinical consideration for patients presenting with scrotal lesion, non-specific clinical presentation, and a history of asbestos exposure and/or long- standing hydrocele.