[C-cells (parafollicular) and medullary cancer of the thyroid gland].

In the human thyroid gland, less than 1% of the cell mass of the organ parenchyma is comprised of C-cells, the typical feature of which is the capacity of produce and accumulate a hypocalcemic hormone, calcitonin. Because of their function, these cells play an important role in the maintenance of homeostasis. Neoplastic proliferation of C-cells results in medullary carcinoma represented by the classical forms and non-medullary apudomas. Morphological, histochemical, and electron microscopic studies demonstrated cytological and histological inhomogeneity of thyroid apudomas and allowed the differential diagnosis criteria for their identification to be outlined.