Non-neural granular cell tumor of the oral cavity

Abstract

Classic granular cell tumors (GCTs) show strong cytoplasmic and nuclear expression of S100 and are believed to be of neural or Schwannian origin. We report a case of intraoral GCT that was negative for S100 but strongly positive for expression of CD10. A 52-year-old woman with a history of hypertension, diabetes, and hypothyroidism presented with an ulcerated, sessile, 1 cm nodule of the left buccal mucosa. The clinical diagnosis was “traumatic fibroma”. Microscopic examination revealed ulcerated fibrovascular connective tissue that contained a cellular population of large, ovoid cells with round, euchromatic nuclei and granular cytoplasm. Pleomorphism was not observed and mitoses were rare. Acute and chronic inflammatory cells were noted throughout the lesion with focal germinal center-like aggregates in the deeper connective tissue. Occasional binucleated and multinucleated and cells, including Touton giant cells, were observed. Immunohistochemical studies revealed the lesional cells to be negative for S100 protein, CD1a, Melan-A, HMB-45, synaptophysin, smooth muscle actin and cytokeratins. CD163 and Factor XIIIa expression was identified among interspersed dendritic cells consistent with histiocytes, however, the granular cells were negative. Lesional cells demonstrated uniformly strong expression of CD10. Besides congenital epulis of the newborn, intraoral examples of non-neural GCT have rarely been described. Non-neural GCT is a diagnosis of exclusion based largely upon immunohistochemical findings and we cannot completely exclude the possibility that this lesion might represent a variant of fibrous histiocytoma.