Immunohistochemical demonstration of lysozyme and lactoferrin in salivary pleomorphic adenomas

Immunohistochemical identification of lysozyme and lactoferrin was made in salivary pleomorphic adenomas (147 cases) and the staining patterns were evaluated with respect to the histological features and histogenesis. In normal salivary glands, the intercalated duct cells gave positive staining for lysozyme in major glands, and serous acinar cells, demilune cells, and interlobular duct cells were positive in minor glands. Lactoferrin staining was irregularly positive in serous cells and ductal epithelium. In pleomorphic adenomas, the reaction for lysozyme was positive in 14% (21/147) of the cases, and was confined to luminal cells of tubulo-ductal structures. Lactoferrin in pleomorphic adenomas was distributed in luminal tumor cells (51%; 75/147), in outer tumor cells (3%; 4/147), and in both luminal and outer tumor cells (5%; 7/147) in tubulo-ductal structures; it was also detected in plasmacytoid myoepithelial cells (5%, 8/147). However, modified myoepithelial cells and other types of neoplastic myoepithelial participants were negative for lactoferrin staining. The occurrence of both lysozyme and lactoferrin in salivary pleomorphic adenomas suggests their participation in the local defense mechanism in the tumor.