Primary pleural epithelioid sarcoma of the proximal type: a diagnostic and therapeutic challenge.

Epithelioid sarcoma (ES) is an uncommon soft tissue neoplasm first described in 1970. It is a unique soft tissue neoplasm of adolescents and younger adults which usually presents as a subcutaneous and deep dermal mass in the distal portions of the extremities. The proximal-type variant of this rare soft tissue neoplasm was only recently reported. The proximal form typically arise in proximal extremities and in the deep parts of pelvis, perineum and genital tract. The proximal type variant has distinct histological characteristics and aggressive clinical course as compared to the distal ES. Inactivation of INI1 has been reported in both distal and proximal variants and can help to make the diagnosis. Furthermore, the proximal variant has a possible association with malignant rhabdoid neoplasm. We describe here a case of primary pleural ES of the proximal type and highlight its diagnostic and therapeutic challenges. 2019 Translational Lung Cancer Research. All rights reserved.