Medullary carcinoma thyroid all EXCEPT: March 2013
**Core Concept**
Medullary carcinoma of the thyroid (MTC) is a type of thyroid cancer that originates from the parafollicular cells, also known as C cells. These cells are responsible for producing calcitonin, a hormone involved in calcium homeostasis.
**Why the Correct Answer is Right**
Medullary carcinoma of the thyroid is characterized by the presence of a specific genetic mutation in the RET proto-oncogene, which leads to the uncontrolled proliferation of C cells. This mutation is often inherited in an autosomal dominant pattern, and patients with a family history of MTC are at higher risk. The primary mechanism of MTC involves the production of calcitonin, which can be used as a tumor marker for diagnosis and follow-up.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because MTC can indeed be associated with the MEN 2A and MEN 2B syndromes, which are characterized by the presence of medullary thyroid carcinoma, pheochromocytoma, and other endocrine tumors.
**Option B:** This option is incorrect because calcitonin is a specific tumor marker for medullary carcinoma of the thyroid, and elevated levels are often used for diagnosis and follow-up.
**Option C:** This option is incorrect because medullary carcinoma of the thyroid is a distinct entity from papillary and follicular thyroid carcinomas, which originate from follicular cells.
**Clinical Pearl / High-Yield Fact**
MTC is often associated with a family history, and patients with a family history of MTC should undergo genetic testing for the RET proto-oncogene mutation.
**Correct Answer: A. This option is incorrect because MTC can indeed be associated with the MEN 2A and MEN 2B syndromes, which are characterized by the presence of medullary thyroid carcinoma, pheochromocytoma, and other endocrine tumors.