Tumor marker related to both colon carcinoma and pancreatic carcinoma: September 2008
**Core Concept**
The question is testing the knowledge of tumor markers associated with specific malignancies. Tumor markers are substances that can be found in higher-than-normal amounts in the blood, urine, or tissues of some patients with certain types of cancer. They can be used for cancer screening, diagnosis, and monitoring treatment response.
**Why the Correct Answer is Right**
The correct answer is CA 19-9. It is a carbohydrate antigen that is produced by the pancreas and is often elevated in patients with pancreatic cancer. However, it is also elevated in patients with colon cancer, particularly those with tumors of the right colon. CA 19-9 is not specific for either cancer, but its elevation can be used as a supportive marker for diagnosis and monitoring disease progression.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as CA 125 is a tumor marker primarily associated with ovarian cancer.
**Option B:** This option is incorrect as CEA (carcinoembryonic antigen) is a tumor marker associated with a variety of cancers, including colorectal cancer, but it is not specific for pancreatic cancer.
**Option C:** This option is incorrect as CA 15-3 is a tumor marker primarily associated with breast cancer.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that tumor markers should not be used in isolation for cancer diagnosis, but rather in conjunction with clinical and imaging findings.
**Correct Answer: C. CA 19-9**