Salivary epithelial-myoepithelial carcinoma: clinical, morphological and molecular features.

Epithelial-myoepithelial carcinoma (EMC) is a rare biphasic tumor accounting for less than 2% of all salivary gland malignancies. It presents as a slowly growing, asymptomatic small size mass, with ulceration of overlying mucosa in some cases. Microscopically, it is characterized by glands lined by the simultaneous presence of two different cell components, inner epithelial cells and outer myoepithelial cells. Immunohistochemical staining of myoepithelial cells is variably positive for vimentin, Smooth Muscle Actin (SMA), Muscle Specific Actin (MSA), S100, Smooth Muscle Myosin Heavy Chain I(SM-MHC), calponin and p63. Several molecular alterations, mainly point mutations, have been described. Mutations of HRAS, AKT1, CTNNB1 and PIK3CA were highlighted in variable percentage of EMC samples. EMC is considered a low-grade malignant tumor with a 5-year survival rate of 94% that may commonly recur locally after resection in 30-50% of cases. At the moment, adequate resection with negative margins is the minimum recommended and necessary treatment.