Mucinous myoepithelial carcinoma of the parotid gland: report of a new histological variant

Mucinous myoepithelial carcinoma (MMC) is a newly recognized histologic variant of myoepithelial carcinoma, and only 14 cases have been reported in the English literature. The authors herein report an additional case of MMC of the parotid gland. A 72-year-old man presented with a right-sided facial mass. Computed tomography demonstrated a 5.6x4.3x2.9 cm soft tissue mass in the right parotid, with peripheral enhancement and internal low-density. Total excision of the right parotid gland was performed. Histologically, the tumor was characterized by proliferation of predominantly mucin-containing signet-ring cells. Many polygonal to plasmacytoid cells with abundant eosinophilic, faintly granular cytoplasm were intermixed with the signet ring cells. Immunohistochemically, the tumor was diffuse positive for CK AE1/AE3, CK7, CK18, S100, and mammaglobin, but negative for CK14, CK20, vimentin, p63, p40, HHF-35, smooth muscle actin, calponin, DOG-1, Sox10, and Wilms' tumor 1 gene protein. The patient's postoperative course was uneventful and he was then lost to follow up.