Mucinous Myoepithelioma, a Recently Described New Myoepithelioma Variant

Myoepithelial neoplasms are tumors composed almost exclusively of cells with myoepithelial differentiation. They frequently contain spindle, plasmacytoid or epithelioid shaped cells and may have oncocytic or clear cytoplasmic features. They are uncommon, accounting for 1.5 % of all salivary gland tumors and for 2.2–5.7 % of major and minor salivary gland tumors, respectively. Recently this author, together with several colleagues, have described three unusual myoepithelial tumors, two benign and one malignant that contained abundant intracellular mucin material, which they termed the mucinous variant of myoepithelioma. This represents a unique, previously undescribed subtype that does not fit in the current classification system. A literature review revealed several similar cases reported as “signet ring-cell” adenocarcinomas of salivary gland, which stained for myoepithelial markers, in addition to containing intracellular mucin material, that are more accurately classified as mucinous myoepithelioma. To date, there are 17 reported mucinous myoepitheliomas; four were classified as benign and 13 as malignant. Thirteen arose in minor salivary glands and four in the parotid gland. One patient presented with a lymph node metastasis. With minimal follow-up currently available, this appears to be a benign to low-grade malignancy.