An electron microscopic study of carcinoid tumors in the middle ears

Abstract

In two cases, carcinoid tumors with primary foci in the middle ear were studied by transmission electron microscopy and the following results were obtained:
1. The tumor nests consisted of large sections with luminal structures, while both peninsular and insular parts made up several tumor cells in the thin sections. No mitotic figure were observed in any of the tumor nests.
2. The tumor cells were classified into 2 types consisting of cells with neurosecretory granules and cells without neurosecretory granules. The ratio of the former to the latter was 10 to 1. The latter were often seen among the insular parts of the tumor nests, while they has a big nucleocytoplasmic ratio, were scarcely present in the intracellular organelles other than the microfilaments and were similar to the basal cells of stratified squamous of pseudostratified columner ciliated epithelia.
3. In the insular parts of the tumor nests, irregular cell arrangement and an unequal nuclear size or obscurity/rupture of the basement membrane were all observed.