Medullary Carcinoma.

Like normal C cells, medullary carcinomas secrete calcitonin, the measurement of which plays an important role

Neuroendocrine cells may secrete VIP, causing diarrhoea

Cases associated with MEN-2A or MEN-2B, in contrast, occur in younger patients and may even arise in children- all MEN-2 positive people carrying RET mutations are offered prophylactic thyroidectomies

Multicentricity is particularly common in familial cases

polygonal to spindle-shaped cells, which may form nests, trabeculae, and even follicles

Acellular amyloid deposits, derived from altered calcitonin- which can be demonstrated by immunohistochemical methods

multicentric C-cell hyperplasia in the surrounding thyroid parenchyma is a characterstic finding in familial .