PLAG1, SOX10, and Myb Expression in Benign and Malignant Salivary Gland Neoplasms

Recent findings in molecular pathology suggest that genetic translocation and/oroverexpression of oncoproteins is important in salivary gland tumorigenesis and diagnosis. Weinvestigated PLAG1, SOX10, and Myb protein expression in various salivary gland neoplasm tissues. A total of 113 cases of surgically resected salivary gland neoplasms at the NationalCancer Center from January 2007 to March 2017 were identified. Immunohistochemical stainingof PLAG1, SOX10, and Myb in tissue samples was performed using tissue microarrays. Among the 113 cases, 82 (72.6%) were benign and 31 (27.4%) were malignant. PLAG1 showednuclear staining and normal parotid gland was not stained. Among 48 cases of pleomorphicadenoma, 29 (60.4%) were positive for PLAG1. All other benign and malignant salivary glandneoplasms were PLAG1-negative. SOX10 showed nuclear staining. In normal salivary gland tissuesSOX10 was expressed in cells of acinus and intercalated ducts. In benign tumors, SOX10 expressionwas observed in all pleomorphic adenoma (48/48), and basal cell adenoma (3/3), but not inother benign tumors. SOX10 positivity was observed in nine of 31 (29.0%) malignant tumors.Myb showed nuclear staining but was not detected in normal parotid glands. Four of 31 (12.9%)malignant tumors showed Myb positivity: three adenoid cystic carcinomas (AdCC) and onemyoepithelial carcinoma with focal AdCC-like histology. PLAG1 expression is specificto pleomorphic adenoma. SOX10 expression is helpful to rule out excretory duct origin tumor,but its diagnostic value is relatively low. Myb is useful for diagnosing AdCC when histology isunclear in the surgical specimen.