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
Rarest type of thyroid carcinoma is 
Select and explain. 
A. Papillary, B. Follicular, C. Medullary, D. Anaplastic
D: Anaplastic
Answer: D: Anaplastic 
Explanation: Undifferentiated (anaplastic) carcinoma
This is one of the most aggressive malignancies in humans. 
Thankfully it is rare. It may develop de novo, or present as dedifferentiation of a papillary or poorly differentiated carcinoma. The disease is characterised by rapid growth, visceral invasion  and  distant  metastases. The  surgeon’s  role  in  this disease is crucial. Thyroid lymphoma can be incorrectly diagnosed as anaplastic cancer and so biopsy is critical. This can be done using a core or open technique.
Reference: Bailey & Love’s short practice of surgery , 27th  ed page no 816