Question 1

Q: Which of the following statements is FALSE regarding medullary cancer of the thyroid?

These cancers take up Radioactive Iodine. ### Explanation **Medullary Thyroid Carcinoma (MTC)** arises from the **parafollicular C-cells**, which are neuroendocrine cells derived from the neural crest. This fundamental embryological origin is the key to understanding its clinical behavior and management. **Why Option D is the Correct (False) Statement:** Radioactive Iodine (RAI) uptake depends on the expression of the Sodium-Iodide Symporter (NIS), which is exclusive to follicular epithelial cells. Since MTC originates from C-cells (not follicular cells), these tumors **do not take up radioactive iodine**. Consequently, RAI ablation is not a therapeutic option for MTC, unlike papillary or follicular thyroid cancers. **Analysis of Other Options:** * **Option A (True):** C-cells naturally produce **Calcitonin**. Elevated serum calcitonin is a highly sensitive and specific tumor marker for MTC, used for both diagnosis and monitoring recurrence. * **Option B (True):** Approximately **20–25%** of MTC cases are familial, occurring as part of **MEN 2A, MEN 2B**, or Familial MTC (FMTC) syndromes, usually due to germline **RET proto-oncogene** mutations. The remaining 75–80% are sporadic. * **Option C (True):** Diarrhea occurs in about **30%** of patients, particularly in advanced or metastatic disease. It is caused by the hypersecretion of calcitonin, prostaglandins, or serotonin, which increases intestinal motility. **High-Yield Clinical Pearls for NEET-PG:** * **Amyloid Stroma:** Histologically, MTC is characterized by nests of cells separated by amyloid deposits (stained by Congo Red). * **CEA:** Carcinoembryonic Antigen is another important tumor marker for MTC. * **Screening:** All patients diagnosed with MTC must be screened for **RET mutations** and **Pheochromocytoma** (before surgery) to rule out MEN 2. * **Treatment:** The primary treatment is Total Thyroidectomy with central compartment neck dissection.

Question

Which of the following statements is FALSE regarding medullary cancer of the thyroid?

Accepted Answer

These cancers take up Radioactive Iodine

Answer

Secrete Calcitonin

Answer

20-25% are familial

Answer

Diarrhea is seen in 30%

Endocrine Surgery — MCQs

Endocrine Surgery — MCQs

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