This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal system, Subject name: Anatomy
Calcitonin is a marker of thyroid 
Select and explain. 
A. Papillary carcinoma, B. Medullary carcinoma, C. Anaplstic carcinoma, D. Adenocarcinoma
B: Medullary carcinoma
Answer: B: Medullary carcinoma 
Explanation: Refer Robbins page no Pg 1030 Medullary Thyroid Carcinomas. Familial medullary thyroid carcinomas occur in multiple endocrine neoplasia type 2 (MEN-2, see later) and are associated with germline RET mutations that lead to constitutive activation of the recep- tor. RET mutations are also seen in approximately one half of nonfamilial (sporadic) medullary thyroid cancers. Chromosomal rearrangements involving RET, such as the RET/PTC translocations repoed in papillary cancers, are not seen in medullary carcinomas.