Abstract
Malignant myoepithelioma is a rare salivary gland carcinoma that might be confused with other neoplastic lesions, including carcinoma and sarcoma. A review of 10 previ ously reported acceptable cases and 2 new ones shows that the tumor affects older individuals with a mean age of 60 years. The parotid gland was the site of tumor in eight cases and the minor salivary glands of the mouth in four. Microscopically, 9 of the 12 tumors were composed either partly or predominantly of spindle-shaped cells. Plasmacytoid cells were the second most common cell type, and round or epithelioid cells were the least common type. Immunohistochemical evidence of myoepithelial differentiation in 10 evaluated cases included positive staining with antibodies against cytokeratin, muscle specific actin, S 100 protein, and vimentin. Ultrastructural features of a myoepithelial phenotype in nine studied cases were cytoplasmic microfilaments with focal densities, desmosomal cell junctions, basal lamina, and hemidesmosomal junctional plaques. Because of a limited number of reported cases and a paucity of follow-up data, it is not possible at present to accurately predict the clinical course of malignant myoepithelioma of salivary glands. However, it appears that local recurrence is an important cause of treatment failure. Metastasis is infrequent. Int J Surg Pathol 2(2):133-140, 1994
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