A Case of Malignant Myoepithelioma Arising in the Submandibular Gland.

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Malignant myoepithelioma (MME) is a rare tumor of the salivary gland accountig for about 0.45% of all salivary gland tumors. An 81 year-old woman with a malignant myoepithelioma originating from the submandibular gland is reported. The patient had recurrent tumors 3 times, and was treated with irradiation against the locally recurrent lesions in the cervical lymph nodes and complete response was obtained. However, she subsequently suffered multiple metastases to the lung. Histologically, the tumor mainly consisted of plasmacytoid cells proliferating in an acinar fashion. Immunohistochemical investigation revealed the carcinoma cells were positive for S-100 protein, vimentin and keratin, and were slightly positive for α smooth muscle actin (αSMA). The carcinoma cells also had high positivity for p53 and MiB-1 (Ki-67).Thirty-five cases of MME had been reported in Japan. Although the therapeutic methods were different, younger patients tended to have a worse prognosis. High positivity for p53 and (or) MiB-1 (Ki-67) suggest a poor clinical outcome. Surgical excision is the mainstay of the therapy for MME, and radiation therapy for recurrent lesions and as a postoperative therapy of MME has been reported to be effective, although radiation therapy per se is still controversial.