Vulvar granular cell tumors with pseudocarcinomatous hyperplasia: a comparative analysis with well-differentiated squamous carcinoma.

The clinical and pathological findings in 10 cases of vulvar granular cell tumor are reviewed. Nine patients presented with solitary, grossly circumscribed, subcutaneous or submucosal nodules and one with synchronous bilateral labial nodules; two exhibited surface epithelial ulceration. Striking pseudocarcinomatous hyperplasia of the overlying squamous epithelium was noted in five of the 10 cases, leading to a misdiagnosis of invasive squamous carcinoma on superficial biopsy in one case. In contrast to previously published data, it was found that pseudocarcinomatous hyperplasia contained numerous mitotic figures, squamous pearls, mildly atypical nuclei, focally prominent nucleoli, and focal single cell infiltration; follicular infundibula were not preferentially involved. Excluding the presence of the underlying granular cell tumor, these features rendered the hyperplastic proliferation nearly indistinguishable from infiltrative squamous carcinoma. Marked squamous cell atypia, although not always present in biopsies of well-differentiated squamous carcinoma, was the only distinguishing histologic feature not found in pseudocarcinomatous hyperplasia. Although vulvar granular cell tumor is an unusual neoplasm, it should be considered in the differential diagnosis of an apparently infiltrative squamous lesion of the vulva when the base of the lesion is not present in the biopsy specimen. This is particularly true of tumors with a nodular, radially symmetric gross appearance.