A case of benign fibrous histiocytoma of the floor of the mouth

Abstract

Benign fibrous histiocytoma occurs predominantly on sun-exposed skin, and rarely arises in the oral cavity. A case of benign fibrous histiocytoma arising in the floor of the mouth is reported. A 67-year-old man was referred to our hospital because of a painless small mass on the right side of the floor of the mouth. Clinical examination revealed a papillary tumor 8 × 8 mm in diameter on the floor of the mouth. The clinical diagnosis was fibroma, and an excisional biopsy was performed. Microscopically, the surgical specimen consisted of uniform spindle-shaped cells arranged in a storiform pattern. There was no evidence of cellular atypia or mitotic figures. Immunohistochemically, the tumor cells were negative for actin (HHF-35) and CD34. The Ki-67 index was less than 10 %. On the basis of these findings, the tumor was diagnosed to be a benign fibrous histiocytoma. No recurrence has been noted as of 1 year after surgery.