Odontogenic sarcoma with smooth muscle differentiation: Report of a case and review of the literature

A case of odontogenic sarcoma with smooth muscle differentiation arising in a 70-year-old woman is described. The lesion grew out of an extraction socket and enlarged rapidly. Radiographically, a large radiolucent lesion with ill-defined margins was observed in the left posterior mandible. Histopathologically, islands of odontogenic epithelium with a surrounding malignant mesenchymal proliferation were noted. The latter exhibited hyperchromatic oval and spindle-shaped cells with 3–4 mitoses in some high-power fields and foci of necrosis. Lesional cells demonstrated immunoreactivity with vimentin and alpha smooth muscle actin, but were negative for antibodies directed against S100, CD34 and CD31. Cytokeratins highlighted the epithelial islands, but did not react with the mesenchymal proliferation. To date, fewer than 70 cases of odontogenic sarcoma have been described in the literature. To our knowledge, this is the first report of an odontogenic malignancy showing smooth muscle differentiation.