This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid Tumor, Subject name: Pathology
Amyloid depostion and raised serum calcitonin levels are seen in which thyroid tumor? 
Select and explain. 
A. Papillary carcinoma, B. Follicular carcinoma, C. Medullary carcinoma, D. Anaplastic carcinoma
C: Medullary carcinoma
Answer: C: Medullary carcinoma 
Explanation: Acellular amyloid deposits derived from calcitonin polypeptides are present in stroma in many cases of medullary thyroid carcinoma. Calcitonin is readily demonstrable within cytoplasm of tumor cells & stromal amyloid by immunohistochemical methods. In addition to circulating calcitonin, secretion of carcinoembryonic antigen by neoplastic cells is useful biomarker, especially for presurgical assessment of tumor load & in calcitonin-negative tumors.