Thyroid, Medullary carcinoma

Medullary thyroid carcinoma is derived from the parafollicular cells, or C cells, of the thyroid. Familial cases are associated with germline RET mutations, are often multicentric and bilateral, and often are also characterized by the presence of C-cell hyperplasia. Microscopically, medullary thyroid carcinoma is composed of polygonal to spindle-shaped cells, which form nests, trabeculae and follicles, that are separated by acellular amyloid derived from calcitonin polypeptide. Medullary thyroid carcinoma positively stains for calcitonin and neuroendocrine tumour markers (chromogranin, synaptophysin, CD56).