GRANULAR CELL TUMOR S-100 NEGATIVE VARIANT

Abstract

Granular cell tumor is a benign mesenchymal lesion that occurs more often in the oral cavity and skin. Its cell origin is controversial, including muscle, fibroblasts, neural crest, neural sheath and histiocytes. Granular cell tumors composed of larger and polygonal cells with abundant eosinophilic granular cytoplasm. Classic granular cell tumor shows positive immunostaining for S-100 and vimentin, and in some cases, positive CD68 staining is also reported positive. However, three cases of S100 negative granular cell tumor in oral mucosa and several cases in skin have also been reported in the literature recently. Therefore, the purpose of this study is to report a case of oral S100 negative granular cell tumor to increase the awareness of this entity. A 79-year-old female patient presented with a small asymptomatic, circumscribed mass lesion in the posterior lateral aspect of the palatal torus. Histologically, the specimen was covered by keratinized stratified squamous epithelium showing no pseudoepitheliomatous hyperplasia. The lamina propria consisted of fibrous connective tissue with chronic inflammation and cluster or sheet of large polygonal cells with granular cytoplasm. Immunohistochemistry showed that the granular cells stain positive for CD68 but negative for S100. Currently there is no difference in recommended treatment or in prognosis of S100 negative from S100 positive granular cell tumor. However, it is important to be aware of this rare variant of granular cell tumor for stablishing correct diagnosis.