Tumor marker for choriocarcinoma :
**Core Concept**
The question is testing knowledge of tumor markers, specifically those associated with **choriocarcinoma**, a type of **gestational trophoblastic disease**. Tumor markers are substances that can be found in higher-than-normal amounts in the blood, urine, or tissues of patients with certain types of cancer.
**Why the Correct Answer is Right**
**Human chorionic gonadotropin (hCG)** is the correct tumor marker for choriocarcinoma. This is because choriocarcinoma is a malignancy of the trophoblastic cells, which are the same cells that produce hCG during a normal pregnancy. Elevated levels of hCG are a hallmark of this disease, and the marker is used for both diagnosis and monitoring of treatment response.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not specified, but typically other options might include markers like **CA-125** for ovarian cancer or **CEA** for colorectal cancer, which are not directly related to choriocarcinoma.
**Option B:** Similarly, this would be incorrect as it does not represent hCG.
**Option D:** This option is also incorrect as it does not correspond to the correct tumor marker for choriocarcinoma.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that hCG levels are not only used for diagnosing choriocarcinoma but also for monitoring the effectiveness of treatment and detecting recurrence.
**Correct Answer:** D. hCG