This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
All are true about medullary thyroid carcinoma except: 
Select and explain. 
A. Involves the parafollicular cell, B. Radiosensitive, C. Amyloid stroma is present, D. Elevated level of calcitonin
B: Radiosensitive
Answer: B: Radiosensitive 
Explanation: Answer- B. RadiosensitiveThese are tumours of the parafollicular (C cells) derived from the neural crest.There is a characteristic amyloid stroma.High levels of serum calcitonin and carcinoembryonic antigen are produced medullary tumours.Calcitonin levels fall efter resection and rise again with recurrence making it a valuable tumour marker in the follow up of patients with this disease.Diarrhoea due to 5-hydroxytrptamine or prostaglandins.Tumours are not TSH dependent and do not take up radioactive iodine.