Immunohistochemical study of tenascin in the interstitium of malignant salivary gland tumors

Abstract

Tenascin (TN), an extracellular matrix component, is known to be an embryonic cancer antigen. This antigen is specifically found in the interstitial tissue of breast or lung cancer. This study immunohistochemically analyzed the expression and distribution of TN in the interstitial tissue of malignant salivary gland tumors, for which no detailed reports are available, and attempted to define the significance of TN. The subjects comprised 48 patients with malignant salivary gland tumors, 49 with benign salivary gland tumors, 8 with chronic sialoadenitis, and 20 with normal submandibular glands. In addition, another extracellular matrix component, fibronectin (FN), which has TNbinding properties, was also analyzed. In normal salivary glands, TN was detected in the basal layers of intercalated, striated and excretory ducts and not in serous or mucinous acinar cells, myoepithelial cells, or the stromal tissue. In chronic sialoadenitis, TN was detected in the same sites as in the normal submandibular gland in addition to the interstitial tissue surrounding the striated and excretory ducts. The presence of TN was demonstrated in the interstitial tissue, but not in the parenchyma, of pleomorphic adenomas in 26 of 30 patients (86.4%). For malignant salivary gland tumors, TN was detected in the interstitial tissue, but not in the parenchyma, in 45 of 48 patients (93.8%). These findings suggest that TN may be specific to the interstitium of malignant gland tumors. TN was diffusely distributed in the interstitium at the focal point of cancerous invasion and in the border area between cancer nests and normal tissue. Comparson of the appearance and distribution of TN and FN, suggested that TN may contribute to the proliferation and invasion of malignant salivary gland tumors. The higher the histological malignancy, the higher was the detection rate of TN in the interstitial tissue of adenoid cystic carcinomas and mucoepidermoid carcinomas, suggesting that TN may objectively reflect the histological malignancy of malignant salivary gland tumors. In addition, the rate of highly positive TN in the interstitium increased parallel to higher grades of malignancy, suggesting that TN may also be a useful indicator of the biological malignancy of malignant salivary gland tumors.