This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid Malignancies, Subject name: Surgery
Most common malignancy of the endocrine system? 
Select and explain. 
A. Thyroid cancer, B. Pancreatic cancer, C. Pituitary adenoma, D. Adrenal malignancy
A: Thyroid cancer
Answer: A: Thyroid cancer 
Explanation: Ans. (a) Thyroid cancerRef: Harrison 18th ed. / 341* Thyroid carcinoma is the most common malignancy of the endocrine system.* Differentiated tumors, such as papillary thyroid cancer (PTC) or follicular thyroid cancer (FTC), are often curable, and the prognosis is good for patients identified with early-stage disease.* In contrast, anaplastic thyroid cancer (ATC) is aggressive, responds poorly to treatment, and is associated with a bleak prognosis.