<prompt> Which of the following is true regarding medullary carcinoma of the thyroid -Arises from parafollicular cellsSecretes calcitoninOccurs in familiesAll  <response>: Ans. is a Arises from parafollicular cells, b Secretes calcitonin, c Occurs in families Medullary Ca of thyroid are neuroendocrine neoplasms derived from the calcitonin secreting parafollicular cells C cells of thyroid which in turn are derived from the ultimobranchial bodies These C cells are concentrated superlaterally in the thyroid lobes, which is where MTC usually develops Most MTCs 75-80 arise sporadically. The remainder occurs in the setting of MEN syndromes 2A or 2B or as familial tumors without an associated MEN syndrome. - The sporadic MTCs tend to originate in one lobe, whereas bilaterality and multicentricity is common in familial cases. The familial cases are also associated with C-cell hyperplasia, which is considered premalignant lesion of MTC. - Familial cases occur at a younger age, even childhood. Sporadic cases are seen in 6th decade. RET proto-oncogenes are known to play an impoant role in the development of both familial sporadic MTCs. Patients with MTC often present with a neck mass that may be associated with palpable cervical lymphadenopathy early spread to lymphatics is common Diarrhoea is a feature in 30 of cases and this may be due to 5-hydroxytryptamine or prostaglandins produced by the tumour cells. Ref B L 25e p797 Distal blood-borne metastasis to the liver, bone frequently osteoblastic, and lung occur late in the disease. Diagnosis is established by FNAC - presence of amyloid stroma is diagnostic. raised serum calcitonin and CEA levels Calcitonin is a more sensitive tumor marker, but CEA is a better predictor of prognosis As it is not possible to distinguish sporadic from familial disease at initial presentation, all new patients with MTC should be screened for RET point mutations - pheochromocytoma 24 hr urinary levels of VMA, catecholamine metanephrine - hyperparathyroidism serum calcium It is impoant to rule out a coexisting pheochromocytoma to avoid precipitating a hypeensive crisis death during surgery Also remember - MTC tumors dont take up radioiodine and are not hormone dependent. 