Which of the following is not true about medullary carcinoma of thyroid?

Ans. is 'd' i.e., FNAC cannot be used for diagnosis 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 (20 - 25%) 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 bilateralityand 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 important 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 25th/e p.797)* Distal blood-borne metastasis to the liver, bone (frequently osteoblastic), and lung occur late in the disease.* Diagnosis is established by:a) FNAC - presence of amyloid stroma is diagnostic.b) raised serum calcitonin and CEA levels (Calcitonin is a more sensitive tumor marker, but CEA is a better predictor of prognosis)c) 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 important to rule out a coexisting pheochromocytoma to avoid precipitating a hypertensive crisis & death during surgery)Also remember* MTC tumors don't take up radioiodine and are not hormone dependent