<prompt> Treatment of choice for medullary carcinoma thyroidTotal thyroidectomyPartial thyroidectomySubtotal thyroidectomyRadioactive ablation  <response>: Ans a Total thyroidectomy Ref Bailey 25th ed 797Medullary carcinomaTumors of parafollicular cells derived from the neural crest. Amyloid stroma is characteristic.High levels of CEA calcitonin useful for follow upDiarrhoea 30 due to 5 - hydroxy tryptamine or PG10 - 20 case familialMEN 2A - Med carcinoma thyroid hyperparathyroidism phaeochromocytoma adrenalMEN 2B - MEN 2A mucosal neuromas marfanoid habitusLymphnode involvement in 50 - 60 casesBlood bom mets commonTumor is not TSH dependent and do not take radioactive iodine.TreatmentTotal thyroidectomy either prophylactic or therapeutic resection of the central bilateral cervical nodes.Familial casesGenetically screened for RET proto oncogene along with S.calcitonin levels.Prophylactic surgery is now recommended for infants with genetic traits.Surgical cases should exclude phaeochromocytoma with urinary catecholamine levelsMost common thyroid cancer - Papillary CaBest prognosis is for Papillary CaClassification of thyroid neoplasmBenignFollicular adenomaMalignantPrimaryFollicular epithelial differentiated - follicular papillaryFollicular epithelial undifferentiated - AnaplasticParafollicular cells - MedullaryLymphoid cells - LymphomaSecondaryMetastaticLocal infiltration 