Elastosis in benign and malignant salivary gland tumors. A histochemical and ultrastructural study

One hundred sixteen cases of various types of salivary gland tumors were examined for the presence of elastic tissue. Almost all the pleomorphic adenomas (97%) and all the malignant pleomorphic adenomas contained elastic tissue in varying amounts. A high percentage (82%) of adenoid cystic carcinomas also contained elastic tissue but the overall quantity was significantly less than in pleomorphic adenomas. All other salivary gland tumors studied, i.e. adenolymphomas, oxyphilic adenomas, mucoepidermoid tumor, and various variants of monomorphic adenomas, were devoid of significant elastic tissue. At the ultrastructural level, the elastic fibers were mainly seen close to neoplastic myoepithelial-like cells, and all stages of elastogenesis were present, ranging from young elastic fibers with a high microfibrilelastin ratio, usually associated with basal-membrane-like material, to mature fibers consisting mainly of an amorphous electron lucent central elastin component. It is postulated that elastic tissue in the salivary gland tumors is produced by the myoepithelial-like tumor cells rather than by tumor stromal induction as has been described in some types of breast carcinomas.