<prompt> A biopsy from a mass in the neck region revels the presence of parafollicular cells. Which of the following is the best marker for the follow up of this patient?CalcitoninThyroglobulinT4T3  <response>: Medullary Ca Arises from parafollicular cells or C cells Associated with secretion of calcitonin. Associated with amyloid deposition. Standard marker is Calcitonin. In calcitonin negative medullary thyroid Ca - Tumor marker is carcinoembryonic Ag Familial medullary thyroid carcinomas In MEN-2 Associated with germline RET mutations-Constitutive activation of the receptor. RET mutations are also in nonfamilial sporadic medullary thyroid cancers. 