Primary leiomyosarcoma in the floor of mouth: a case report.

Leiomyosarcoma (LMS) is a malignant soft tissue tumor that exhibits smooth muscle differentiation, and its occurrence in the oral cavity is exceedingly rare, especially in the floor of mouth. A 54-year-old male was admitted for evaluation of a painless nodular mass in the left floor of mouth with a 3-month history. With the help of computed tomography (CT) and magnetic resonance imaging (MRI) examination, the patient went on a surgery excision, and by pathological and immunohistochemical findings, a diagnoses of LMS was confirmed. Then the patient went on chemotherapy, and six-month follow up showed no recurrence of cancer. The diagnosis of LMS is difficult to be made, and it is usually confirmed by immunohistochemical stains, such as positive for smooth muscle actin (SMA), vimentin, and Ki-67.