Myoepithelioma-Like Tumor of the Vulvar Region: A Clinicopathologic Study of Four Cases.

Abstract

Myoepithelioma-like tumors of the vulvar region (MELTVR) are solid tumors found in the vulva of adult women. They have a similar histopathology to myoepithelioma but differ in immunohistochemical phenotype and genetic changes. In this study, we report four examples of MELTVR, occurred in the external genitalia and mons pubis of adult women aged 32 to 39 years. The tumors presented as subcutaneous masses without obvious tenderness. The tumors were composed of a mixture of myxoid and nonmyxoid components, and myxoid areas accounted for 5% to 80% of the tumor volume. The tumor cells were spindle-shaped or epithelioid, with abundant cytoplasm, vesicular nuclei, and small nucleoli. The nuclear atypia was mild to moderate, with 0 to 10 mitotic figures per 10 high-power fields. Immunohistochemically, all four tumors showed consistent positivity for EMA, calponin and ER; three tumors exhibited PR expression. All tumors were negative for S100 protein and SMA. AE1/AE3 expression was absent in all except one tumor, which showed rare positivity. SMARCB1/INI1 expression was deficient in all tumors. EWSR1 and FUS rearrangements were absent. All tumors were treated through surgery. All patients were alive without recurrence on most recent follow-up. Together, this overview of four additional tumors of MELTVR offers further insight into this rare and poorly understood disease.