Metastatic Granular Cell Tumor of the Vulva With CHEK2 Mutation: A Case Report and Molecular Insights

Granular cell tumors (GCTs) are rare neoplasms, typically of Schwannian origin, with generally a benign and indolent clinical behavior. However, a small subset exhibits malignant behavior, often without clear histologic features. We report a rare case of a vulvar granular cell tumor in a 21-yr-old woman with subsequent pulmonary metastasis. The patient presented with a slowly growing vulvar nodule and a subcutaneous lesion on the left flank. Imaging studies revealed residual disease in the vulva and a suspicious lung nodule, both of which were surgically resected. Histopathologic examination confirmed features consistent with granular cell tumor in both primary and metastatic sites, despite the absence of cytologic atypia, necrosis, or elevated mitotic activity. Immunohistochemistry revealed positivity for S100, CD68, NSE, and inhibin, with a low Ki-67 index (