Myoepithelial carcinoma of pharynx expressing KIT and PDGFRA

KIT and PDGFRA expression has rarely been examined in myoepithelial carcinoma (MC) of the salivary glands. An 89-year-old Japanese woman presented with a pharyngeal mass. Gross and imaging examinations revealed an elevated mass in the middle pharynx next to the oral cavity. A biopsy revealed atypical cells, and tumorectomy was performed. The tumor was composed of atypical epithelioid cells arranged in solid nests, cords, and vague acinar patterns. Mitotic figures were recognized in 3 per 50 high power fields. Immunohistochemically, the tumor cells were positive for myoepithelial markers including cytokeratin (CK) 14, α-smooth muscle antigen, S100 protein, and p63. They were also positive for KIT, PDGFRA, pancytokeratin AE1/3, CK34βE12, CK5/6, vimentin, p53, and Ki-67 (labeling=28%). They were negative for neuron-specific enolase, CD45, CD34, CD56, chromogranin, synaptophysin, melanosome, desmin, epithelial membrane antigen, CK18, CK20, pancytokeratin (CAM5.2). A pathologic diagnosis of myoepithelial carcinoma arising from minor salivary glands was made. No metastatic lesions were found by various imaging techniques. The patient is now receiving palliative radiation therapy 2 months after the operation. The present case showed that MC can express KIT and PDGFRA.