Immunolocalization of interleukin-6 in salivary gland tumors

Interleukin-6 (IL-6) is a multifunctional cytokine that regulates immune responses and acute phase reactions. It has demonstrated a growth factor function in several tumors, including those of salivary, plasma cell, and renal origin. We performed immunohistochemical staining for IL-6 localization on 57 salivary tumors. Reactivity was scored by intensity (0 to 4+) and percentage of cells staining, and the tumors were classified into three groups representing low (0 to 1+, 0% to 30%), moderate (2 to 3+, 31% to 75%), or high (> 3 to 4+, 76% to 100%) reactors. High reactivity was found in all primary pleomorphic adenomas (N = 10), five of eight recurrent pleomorphic adenomas, and all polymorphous low grade adenocarcinomas (N = 4). Moderate reactivity was observed in four of seven basal cell adenomas and three of five myoepitheliomas. Low reactivity characterized all acinic cell carcinomas (N = 3) and mucoepidermoid carcinomas (N = 3) as well as six of nine primary adenoid cystic carcinomas and all metastatic adenoid cystic carcinomas (N = 3). Carcinoma ex pleomorphic adenoma (N = 5) had three low and two moderate reactors. A pattern emerged in which the benign and low grade malignant tumors showed stronger reactivity than the metastatic or high grade malignant tumors. This suggests an inverse relationship between the presence of IL-6 and the biological aggressiveness of salivary gland tumors. The function of IL-6 in salivary gland neoplasia awaits further study and elucidation.