All of the following are tumour markers, except –
**Core Concept**
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. These markers can be used to help diagnose cancer, determine the stage of cancer, and monitor the response to treatment.
**Why the Correct Answer is Right**
The correct answer is a substance that is not typically associated with tumor growth or cancer progression. Tumor markers are often proteins, enzymes, or hormones produced by cancer cells or in response to cancer. They can be used to monitor the disease and make treatment decisions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a commonly used tumor marker for several types of cancer, including colon, breast, and lung cancer. It is a protein produced by cancer cells and can be detected in the blood or tissues of patients with these cancers.
**Option B:** This option is incorrect because it is a tumor marker for several types of cancer, including prostate, lung, and breast cancer. It is a protein produced by cancer cells and can be detected in the blood or tissues of patients with these cancers.
**Option C:** This option is incorrect because it is a tumor marker for several types of cancer, including ovarian, breast, and lung cancer. It is a protein produced by cancer cells and can be detected in the blood or tissues of patients with these cancers.
**Clinical Pearl / High-Yield Fact**
Some tumor markers, such as CEA (carcinoembryonic antigen), are not specific to a particular type of cancer and can be elevated in patients with non-cancerous conditions, such as inflammatory bowel disease or pancreatic disease. Therefore, it is essential to interpret tumor marker results in the context of a patient's medical history and other diagnostic tests.
**Correct Answer: D.**