Adenoma of the Parotid Salivary Gland: Onkocyte Tumor

Abstract

Among the neoplastic diseases of the parotid gland, tumors of the so-called mixed salivary gland type predominate. The histogenesis of these peculiar new growths has been a topic of unremitting discussion, the derivation of the various cell and tissue complexes which compose their histologic pattern still being explained by a number of divergent theories. Some authors believe these growths to be true mixed tumors originating from pluripotent embryonic cells of branchial rests (Cohnheim); others sponsor a theory of mesenchymal-endothelial origin, while still others explain them as epiblastic tumors, i.e. as adenomas of the glandular epithelium. In this latter case the so-called stroma is regarded as the product of an inverted secretory activity of the tumor cells (Masson), or as due to metaplasia of the neoplastic epithelium (Ehrich), or, in accordance with the suggestion of Stein and Geschickter (1), as the result of the inclusion of primitive connective tissue within the neoplasm at an early stage of its development. Benign tumors of the parotid gland without a stroma, so characteristic of these mixed tumors, are apparently uncommon. McFarland (2) found in his series of 151 benign parotid tumors only one in which the stroma was entirely lacking. In view of the great variability of the histologic pattern of these neoplasms, however, he hesitated to classify this single, apparently purely epithelial tumor, as a true adenoma, and suggested that most, if not all, so-called adenomas of the parotid gland are mixed tumors in which all other tissue elements have been supplanted by cells of the epithelial type.