USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

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Which tumor derives from C cells and is associated with calcitonin as a tumor marker?

Primary B-cell lymphoma
Medullary carcinoma
Neuroblastoma
Primary hyperparathyroidism

The correct answer is: Medullary carcinoma

The correct answer is medullary carcinoma. This type of tumor originates from the parafollicular C cells of the thyroid gland, which are responsible for producing the hormone calcitonin. Calcitonin plays a role in regulating calcium levels in the blood by lowering them when necessary, and its elevated levels can be an important marker for diagnosing medullary thyroid carcinoma. This association with calcitonin is a key distinguishing feature of medullary carcinoma. The other conditions listed are not driven by C cells or associated with calcitonin production. Primary B-cell lymphoma primarily involves the lymphatic system and does not have a specific link to calcitonin. Neuroblastoma is a type of cancer typically arising from adrenal medullary tissue or sympathetic ganglia, and it is associated with different tumor markers such as catecholamines, not calcitonin. Primary hyperparathyroidism is mainly characterized by increased parathyroid hormone levels due to parathyroid gland tumor activity, and it is not related to C cells or calcitonin. Therefore, medullary carcinoma is the only option correctly linked to C cells and calcitonin production.