Clear cell variant of superficial cutaneous leiomyosarcoma associated with RB1 mutation: clinical, dermoscopic, and histopathological characteristics.

Leiomyosarcoma is a relatively rare soft tissue tumor whose clear cell variant has only been reported in leiomyosarcomas of the uterus. We report here for the first time a primary cutaneous clear-cell leiomyosarcoma in the trunk skin of a 49-year-old man, characterized by a very indolent clinical and dermoscopic presentation, mimicking a dermatofibroma. Genetic analysis of the otherwise healthy patient revealed a germline mutation in the retinoblastoma 1 gene (RB1); the same mutation was found in his son, who had previously developed retinoblastoma. Moreover, the mother of the patient had died of uterine leiomyosarcoma with clear-cell changes. Mutations in the RB1 gene occur commonly in human neoplasms. In this patient, we were able to link his clear cell variant of cutaneous leiomyosarcoma with the loss of retinoblastoma protein expression, as revealed by immunohistochemical staining analysis. This article is protected by copyright. All rights reserved.