Malignant Myoepithelioma of Minor Salivary Gland Origin

Myoepithelial cells are a significant component of most types of salivary gland tumors. A small but increasing number of case reports have also shown that true myoepithelioma (ME) forms a distinct clinicopathologic entity of salivary gland tumors with unique histologic features, however, the malignant type of ME is exceedingly rare. The present paper reports a case of malignant ME originating from the palatal minor salivary gland. The patient was a 70 year old Japanese male with recurrent tumor of the palatal region. Pathologically, the tumor consisted of proliferating polygonal shaped cells and plump spindle cells with cellular atypia and frequent mitoses, forming lumen less lobuli or strands. Clear tumor cells were also found in part. The stroma was poorly developed without any myxoid or chondroid features. Immunohistochemical study showed positive stainings for S 100 protein, actin and vimentin in the tumor cells. Ultrastructurally, tumor cells had features of myoepithelial cells.