Histopathological study of oncocytes in the human labial salivary glands

Abstract

Oncocytes are characterized under light microscope by swollen cytoplasm with acidophilic and granular appearence and frequently by pyknotic nuclei. These cells can be found not only in salivary glands and other exocrine and endocrine organs but also in some tumors. Generally, oncocytes appear to increase in frequency with advancing age, but their genesis and biologic significance remain still obscure. In this study, the appearence and the histological pattern of oncocytes in the human labial salivary glands were systematically examined, and the possible mode of development and the significance of these cells were also discussed. One hundred cases of the labial salivary glands were randomly collected from autopsies, and serial sections were made. The designation of oncocytes was in accordance with Hamperl's description. The results were as follows;1) Oncocytes were found in 85 cases (85.0%), ranging in age from two to 93. Although oncocytes occurred in greater number in elder cases, oncocytes were found in 50-to-70% of those who was under forty. The frequency was slightly higher in females than in males. 2) The frequent presence of oncocyte was noted in the duct systems, especially in the interlobular, intralobular and main excretory ducts. 3) In both acini and ducts, oncocytes were generally gathered in small groups but also occurred singly. Therefore, all of these epithelial elements ofthe salivary glands may be able to transform into oncocytes. 4) When oncocytes were found in moderately to heavy concentration, the oncocytes stratified in papillary projection, adenomatous pattern, conglomeration microtubular structures, etc., and it is thought that these findings suggest proliferative disposition of oncocytes. The highest changes of these were found in 8 cases of 50 to 70 years old. 5) There was no definite correlation between oncocytic changes and fibrosis, atrophy with fatty replacement, regenerative process due to radiation or lymphoid cell infiltration, etc. 6) From the above-mentioned light microscopic findings of oncocytes in the human labial salivary glands, it is assumed that the occurrence of oncocytic changes have some relationship with the aging. However, oncocytic changes may not be the result of degenerative one of the salivary glands associated with aging. 7) Under electron microscopy, the cytoplasm of oncocyte was completely filled with nonoriented mitochondria of various sizes and shapes. Moreover, the cristae of mitochondria were markedly increased in number and in length, and there were no intramitochondrial granules. Organellae, other than mitochondria, were sparse.As a results of this investigation and review of various reference literature, a hypothesis is put foward that the significance of oncocytes is a manifestation trying to compensate for functional defects by an increased number of mitochondria and the surface area of menbrane. The mitochondrial proliferation may occur in the abscence of obvious functional needs. Another possibility is that the oncocytic transformation represents a “mitochondrial disease” or “mitochondriopathia” of epithelial cells. The determination of the function of oncocytes willrequire more specific physiological and biochemical studies. And it must be decided whether oncocytes occurring in normal salivary glands and tumors are same cytological characteristics or not.