This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid, Subject name: Surgery
Least common thyroid malignancy is: 
Select and explain. 
A. Papillary, B. Follicular, C. Medullary, D. Anaplastic
D: Anaplastic
Answer: D: Anaplastic 
Explanation: Least common thyroid malignancy is anaplastic. Most common thyroid malignancy - Papillary > Follicular > Medullary > Anaplastic Papillary carcinoma - 80% occur in Iodine-sufficient areas and predominant thyroid cancer in children and individuals exposed to external radiation. Follicular carcinomas - 10% of thyroid cancers and occur more commonly in iodine-deficient areas. MTC- about 5% Anaplastic carcinoma- about 1%