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: Pathology
[{'content': 'Medullary carcinoma of thyroid is associated with which of the following gene defect? \nSelect and explain. \nA. Ret Proto Oncogene, B. FAP gene, C. Rb gene, D. BRCA 1 gene', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Point mutation in RET proto-oncogene play an impoant role in the development of both familial & sporadic medullary carcinomas. Medullary carcinoma is a neuroendocrine neoplasm of thyroid derived from the parafollicular cells or C-cells of thyroid. It secretes calcitonin. Tumor arise sporadically in 80% cases, remainder is associated with MEN Type IIA Or IIB syndrome. Most common presentation is mass in the neck. Ref: Genetics in Clinical Practice: New Directions for Nursing and Health Care By Dale Halsey Lea, Page 158 ; Robbins Pathologic Basis of Disease 6th Edition, Page 289, 292, 1145-6', 'role': 'assistant'}]