Primary malignant fibrous histiocytoma of the mandible: Report of a rare case with an immunohistochemical analysis

We present a rare case of a malignant fibrous histiocytoma (MFH) arising in the mandible of a 74-year-old Japanese woman. Intraoral examination revealed a single ulcer in the right mandibular alveolar ridge at the molar region. Panoramic radiographs revealed ill-defined radiopaque, radiolucent area in the right molar region. Computed tomography demonstrated a mass with cortical bone destruction. The histological examination revealed numerous fibroblast-like spindle-shaped cells arranged in a fascicular pattern and scattered multinucleated and mononuclear cells with bizarre nuclei throughout the lesion. Moderate nuclear pleomorphism was evident with few mitotic cells. The immunohistochemical techniques proved positive for vimentin of all tumor cells and Ki-67 of about half of the tumor cells and negative for c-kit, CD34, smooth muscle actin, CD68, S100 protein, and Factor VIII of all tumor cells. The lesion was diagnosed as a MFH of storiform-pleomorphic type. After surgical removal of the lesion and the adjacent tissues, the patient was referred to a radiotherapist for continuation of treatment and remains well almost a year later.