A case of granular cell tumor in the floor of the mouth.

Granular cell tumor, which characteristically has eosinophilic granules in the cytoplasm, is a relatively rare lesion in the oral and maxillofacial region. The authors encountered a case of a granular cell tumor arising in the floor of the mouth and investigated the immunohistochemical staining of the tumor. The patient was a 36-year-old man presenting with swelling of the floor of the mouth. Microscopic examination of a biopsy specimen revealed a granular cell tumor, and total resection of the tumor was performed. Histopathological examination disclosed a benign neurogenic tumor, adjacent to the minor salivary glands, which was composed of cells containing oval nuclei and abundant eosinophilic cytoplasm. On immunohistochemical examination of the tumor, the granules in the cytoplasm were positive for PAS staining and the tumor cells were strongly positive for S-100 protein staining. These findings revealed that the lesion was a granular cell tumor derived from Schwann cells.