What is medullary thyroid carcinoma?

5%, neuroendocrine tumors from parafollicular cells/C cells of the thyroid, measurement of calcitonin imp in dx and postop, sporadic (70%), adult between 40-50 yrs, 30% familial in MEN2A/2B (usually young/children), or famlial w/out MEN Solitary nodule/multiple lesions involving both lobes of thyroid, larger lesions contain areas of necrosis/hemorrhage and may extend through thyroid capsule. Micrscopy (polygonal cells, form nests/trabeculae/follicles, amyloid deposits present in stroma in many cases and are distinctive features. Calcitonin seen in cytoplasm of cells, and stromal amyloid is one of the characteristics of medullary carcinoma of multicentric C cell hyperplasia in surrounding thyroid parenchyma (absent in sporadic form) Foci of C cell hyperplasia represent precursor lesion (believed)