Primary leiomyosarcoma of the mandible.

Leiomyosarcoma (LMS) is a malignant soft tissue tumor that exhibits smoothmuscle differentiation. Its occurrence in the oral cavity is exceedingly rare. This article presents a 67-year-old woman with 9-month history of a painful tumoral lesion on the right side of mandible. Tumor was composed of fascicles of spindle-shaped cells with cigar-shaped nuclei and eosinophilic cytoplasm. Immunohistochemistry showed that tumor cells were positive for smooth muscle actin (SMA) and desmin. The findings were consistent with the diagnosis of LMS.