Perineurial malignant peripheral nerve sheath tumor in the setting of multiple soft tissue perineuriomas: A rare presentation of an uncommon tumor

Perineurioma is an uncommon soft tissue tumor with characteristic histological and immunohistochemical features. Herein, this tumor is presented within a rare clinical setting, in a 45-year-old gentleman, with multiple soft tissue swellings and a previous history of surgical excision of a thigh mass. Four years back, he developed multiple soft tissue tumor swellings for which he lately underwent multiple wide excisions, elsewhere that were reported as multiple dermatofibrosarcoma protuberans (DFSPs). Histopathological review of the thigh and axillary tumor showed a perineurioma (EMA+, S100-P-ve, CD34-ve, low MIB1), whereas the recurrent leg mass disclosed a high-grade perineurial malignant peripheral nerve sheath tumor (MPNST) (EMA+, CD56+, S100-P-, high MIB1, CD34-ve, p53+ve). Within four months of post-excision, he developed additional swellings, and died of respiratory insufficiency. This case forms the first documented case of perineurial MPNST with multiple, metachronous soft tissue perineuriomas. Available literature review of perineurial MPNSTs and diagnostic implications are discussed herewith.