system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
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?
assistant
The correct answer is  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.