All are true regarding medullary carcinoma of thyroid except –
**Core Concept**
Medullary carcinoma of the thyroid (MTC) is a type of neuroendocrine tumor that originates from the parafollicular cells (also known as C cells) of the thyroid gland. It is characterized by the presence of calcitonin, a hormone produced by the C cells, in the tumor cells.
**Why the Correct Answer is Right**
MTC often presents with a family history, particularly in the context of Multiple Endocrine Neoplasia (MEN) syndromes, such as MEN 2A and MEN 2B. The tumor cells of MTC express calcitonin and other neuroendocrine markers, such as chromogranin A and synaptophysin. MTC is also known for its aggressive behavior and potential to metastasize to lymph nodes and distant sites.
**Why Each Wrong Option is Incorrect**
**Option A:** MTC is a type of papillary carcinoma. (This is incorrect because MTC is a distinct entity from papillary carcinoma, which originates from the follicular cells of the thyroid gland.)
**Option B:** MTC is associated with thyroid-stimulating hormone (TSH) receptor mutations. (This is incorrect because MTC is not associated with TSH receptor mutations, which are typically seen in follicular and papillary thyroid carcinomas.)
**Option C:** MTC often presents with a rapid growth pattern and aggressive behavior. (This is incorrect because this statement is true for MTC, and it is actually one of the distinguishing features of this tumor type.)
**Clinical Pearl / High-Yield Fact**
MTC is often associated with RET proto-oncogene mutations, which are inherited in an autosomal dominant pattern. This genetic predisposition is an important factor in the development of MTC, particularly in the context of MEN syndromes.
**Correct Answer: A. MTC is a type of papillary carcinoma.**