<prompt> All of the following are true about medullary carcinoma of thyroid exceptIt is tumour arising from C cells derived from the neural crestSecrete high levels of calcitoninIt is not dependent on TSHMost cases are familial  <response>: MEDULLARY CARCINOMA It is an uncommon type it arises from the parafollicular C cells which is derived from ultimobranchial body neural crest blood level of calcitonin is a tumour marker it is not dependant on TSH Most cases are sporadic and a small amount is familial ref ;page no;486 5th edition of SRB;S Manual of SURGERY 