Amyloid depostion and raised serum calcitonin levels are seen in which thyroid tumor?

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.