[Morphology and histochemistry of medullary thyroid carcinomas (author's transl)]

The medullary thyroid carcinoma was characterized as clinicopathological entity by Hazard, Hawk and Crile as early as 1959. As reported in literature the incidence of these tumors ranges from 3.5 to 11.9% of the thyroid carcinomas. In the study presented the morphological, histochemical and electron microscopical investigations in 8 cases of medullary thyroid carcinoma are reported. Different methods are used to demonstrate polysaccharides, proteins, especially polypeptide hormones, and amyloid. Furthermore several silver impregnation techniques for differentiation of argentaffin and argyrophilic cells were performed. The age of the 8 patients ranged from 30 to 65 years, 5 patients were females, the sex ratio of females to males runs to 1.7:1. In 4 cases metastases in regional lymph nodes were found. The tumor tissue preponderately showed a solid-travecular pattern. The tumor cells were seen in cord-like and nest-like arrangement. In places also a typical endocrine structure was present revealing an orientation of cells around capillaries here and there. A differentiation of light and dark cells was possible. Electron microscopically these light microscopical observations could be confirmed: dark cells possessed more organeles than light cells. Infiltrations of blood vessels did not occur, but infiltrations of lymph vessels were the rule. The tumors contained variable amounts of amyloid which could be seen by fluorescence and polarization microscopical methods in fine fiber-like structures or in coarse deposits. At the ultrastructural level typical secretory granules varying in electron density and having a diameter of 220-560 nm were visible. Some light tumor cells exhibited 50-120 A thick fibrils which could not be distinguished from extracellular amyloid fibrils. The histochemical findings evidenced moderately abundant proteins in the cytoplasm of tumor cells. Histochemically the amyloid corresponds to the so-called apudamyloid. A great deal of the proteins is orderly arranged in amyloid whereas this is not the case in the tumor cell cytoplasm as proved by the coupled tetrazonium reaction which was evaluated polarization microscopically. In amyloid tryptophan was absent. The medullary thyroid carcinoma has a low-grade malignancy and, in accordance to other authors, it is to be stated that this tumor is histogenetically related to the parafollicular cells (C-cells). Its distinction from other thyroid tumors is warranted basing on morphological and pathophysiological features. Structural patterns common with those of other endocrine tumors are demonstrable. The findings point to a relationship of medullary thyroid carcinoma with the APUD series or Feyrter's Helle-Zellen-System. Considering the possible simultaneous occurrence of pheochromocytomas and adenomas of the parathyroid gland it must be assumed that the medullary thyroid carcinoma is one of the dysplasias of the neural ectoderm.