A SMARCB1-deficient vulvar neoplasm with prominent myxoid stroma: report of a case showing ERG and FLI1 expression.

In the vulvar region, epithelioid sarcoma (ES) is the most frequent SMARCB1-deficient neoplasm, followed by myoepithelial carcinoma (MC). Previous studies have demonstrated that some SMARCB1-deficient vulvar neoplasms cannot be classified as either ES or MC. Herein, we report of a 42-year-old woman with a SMARCB1-deficient neoplasm with prominent myxoid stroma in the vulva. It contained both epithelioid and spindled tumor cells, both of which showed vimentin and EMA expression. Although other markers useful for the differential diagnosis among SMARCB1-deficient tumors were negative, this tumor displayed characteristic expression of ERG and FLI1. As there are no reliable data regarding expression of ERG and FLI1 in MC, which are demonstrated to be often expressed in ES, further classification of cases such as the one reported here requires reliable data regarding their expression status in MC.