**Question:** True about tumour marker is -

A. Tumour markers are always specific to a particular cancer type
B. Tumour markers are elevated in all types of cancer
C. Tumour markers are specific to a particular cancer type and not affected by other factors
D. Tumour markers are elevated in healthy individuals and do not correlate with cancer stage or progression

**Correct Answer:** C. Tumour markers are specific to a particular cancer type and not affected by other factors

**Core Concept:** Tumour markers are biological substances that are produced in response to the presence of cancer cells or other abnormal cell growth. They can be used as diagnostic, prognostic, or monitoring tools in oncology.

**Why the Correct Answer is Right:** Tumour markers are specific to particular cancer types or conditions because they are produced by the abnormal cells or tissues. For example, carcinoembryonic antigen (CEA) is raised in colorectal cancer, alpha-fetoprotein (AFP) is elevated in hepatocellular carcinoma, and prostate-specific antigen (PSA) is increased in prostate cancer. These markers are not affected by other factors, such as inflammation, infection, or benign conditions, as they are cancer-specific.

**Why Each Wrong Option is Incorrect:**

A. False - Tumour markers are not specific to a particular cancer type. They are produced by cancer cells or tissues, but not all cancer types will produce the same marker.

B. False - Tumour markers can be elevated in some benign conditions or normal physiological processes, making them less reliable in diagnosing cancer.

D. False - Tumour markers' levels can change with cancer stage, progression, or treatment, making them valuable for monitoring purposes. However, they are not elevated in healthy individuals.

**Clinical Pearl:** Tumour markers are essential in oncology for cancer diagnosis, prognosis, and monitoring treatment response. They are often used in conjunction with clinical symptoms, imaging studies, and tissue biopsy for a comprehensive cancer evaluation. Early detection and monitoring of tumour markers can help guide treatment decisions and improve patient outcomes.