Abstract
Two typical adenolymphomas of the parotid gland were studied with respect to the ultrastructure of their epithelial component. The neoplastic epithelium consisted of “oncocytes” which were arranged in double-layered or pseudostratified fashion. Their cytoplasm was almost totally packed with a large number of hypertrophic mitochondria showing a variety of peculiar forms as previously described and complete absence of intramitochondrial granules. Two types of oncocytes were distinguished, i. e., typical oncocytes with vesicular nuclei and condensed oncocytes with pyknotic nuclei and more degenerated, fused mitochondria. Columnar apical cells frequently contained well-developed actin-like microfilaments and numerous dense bodies identified as lysosmes owing to their acid phosphatase activity. The possible role of these microfilaments and lysosomes was discussed in conjunction with apocrine secretion of apical cells. The occurrence of oncocytes with multiple motile cilia at their apical surfaces was revealed in many epoxy blocks examined, and was regarded as representing metaplastic change rather than indicating their branchial origin. Pyramidal or cuboidal basal cells also exhibited the oncocytic features to a lesser degree. The synthesis of lysosomal bodies appeared to take place in these cells. Ultrastructural evidence of the myoepithelial nature of basal cells could not be obtained.
