Marker for carcinoma colon is:September 2005, March 2013
💡 Explanation
## **Core Concept**
The question tests knowledge of tumor markers, specifically for colorectal carcinoma. Tumor markers are substances produced by cancer cells or in response to cancer. They can be used for diagnosing, monitoring, and predicting the outcome of cancer.
## **Why the Correct Answer is Right**
The correct answer, **C. Carcinoembryonic Antigen (CEA)**, is a protein typically found in embryonic endodermal epithelium but not in adult tissues. It is often elevated in various types of cancers, most notably colorectal cancer. CEA is used clinically as a tumor marker for monitoring disease recurrence and response to treatment in patients with colorectal cancer.
## **Why Each Wrong Option is Incorrect**
- **Option A:** *Alpha-fetoprotein (AFP)* is primarily associated with hepatocellular carcinoma and certain germ cell tumors, not colorectal cancer.
- **Option B:** *Human chorionic gonadotropin (hCG)* is elevated in choriocarcinoma, certain germ cell tumors, and some other malignancies but is not a marker for colorectal cancer.
- **Option D:** *Prostate-specific antigen (PSA)* is a marker for prostate cancer, not colorectal cancer.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that while CEA is used as a tumor marker for colorectal cancer, it is not diagnostic on its own due to its elevation in other conditions and not all colorectal cancers producing it. It is mainly used for monitoring disease recurrence.