Cutaneous Metastases From Malignant Mesothelioma of the Tunica Vaginalis Testis

Mesotheliomas are uncommon tumors arising from mesothelial cells lining the serous membranes of the pleura, pericardium, peritoneum, and tunica vaginalis testis. Less than 100 cases arising from the tunica vaginalis testis have been published and, to our knowledge, only 5 cases of cutaneous involvement from these tumors have been reported. We report an additional case with fatal outcome. A 93-year-old man presented with multiple polypoid nodules on the left scrotum. Ulceration was also present, and a firm 5-cm palpable testicular mass was also found. The patient had been exposed to asbestos for 40 years. Histologic examination of a skin biopsy from one of the nodules showed diffuse dermal infiltration of markedly atypical cuboidal cells, with polymorphous and hyperchromatic nuclei. Mitotic figures were common. These cuboidal cells lined clefts, forming a tubular and micropapillary pattern throughout papillary and reticular dermis. Immunohistochemical study showed strong nuclear and cytoplasmic positivity for calretinin, epithelial membrane antigen (cytoplasmic), and cytokeratin-7 (cytoplasmic) and nuclear positivity for Wilms tumor-1. These findings were consistent with cutaneous infiltration from malignant mesothelioma of the tunica vaginalis testis. Treatment of this rare tumor remains challenging because there are currently no recommended guidelines, but radical inguinal orchiectomy is an optimal choice.