Medullary cancer of the thyroid gland and its possible relations to carcinoids. An ultrastructural study.

Abstract

The ultrastructural study of a medullary cancer of the thyroid gland revealed some unusual features. The stroma of the tumor did not contain amyloid. An abundant amount of intracytoplasmic microfilaments was observed in the tumor cells, sometimes displacing the various organelles. The most prominent feature was the presence of very dense, pleomorphic (“biconcave”) secretory granules, measuring an average of 250 mµ in their longest diameter. Mainly because of the type of secretory granules, this tumor showed a peculiar resemblance to ileal carcinoids. The possible significance of this finding is discussed.