SMARCB1 (INI-1) deficient vulvar neoplasms: report of 4 cases with review of literature

SMARCB1 (INI-1) deficient vulvar neoplasms are rare tumors with scarce available literature. These tumors can be comprised of proximal type epithelioid sarcoma (ES), myoepithelial carcinoma (MEC), myoepithelioma-like tumor of the vulvar region (MELTVR), and myxoepithelioid tumor with chordoid features (METC). A subset of vulvar yolk sac tumors (VYSTs) also exhibit INI-1 deficiency. Unlike other vulvar germ cell tumors, some researchers speculate these to be of non-germ cell origin. Herein, we report a spectrum of INI-1 deficient vulvar tumors comprising VYST (1 case), ES (1 case) and MELTVR (2 cases) which showed variable histomorphological features and concomitant lack of INI-1 expression on immunohistochemistry. The clinical course ranges from indolent to aggressive and all tumors warrant close clinical follow up. Management includes surgical excision with or without adjuvant therapy. Recognition of these unique neoplasms can aid in refining the classification scheme for such uncommon vulvar tumors.