A laboratory test is positive for the tumor biomarker PSA. What cancer is the biomarker indicative of?

The tumor biomarker PSA, or Prostate-Specific Antigen, is specifically associated with prostate cancer. PSA is a protein produced by both normal and malignant cells of the prostate gland, and elevated levels of this antigen in the blood can indicate the presence of prostate cancer or other prostate conditions such as benign prostatic hyperplasia or prostatitis.

In the context of the other options, while colon cancer may utilize different biomarkers such as CEA (Carcinoembryonic Antigen), breast cancer employs markers like CA 15-3 or HER2, and thyroid cancer can involve markers such as thyroglobulin or calcitonin, none of these are connected with PSA. This makes PSA a distinct and important marker specifically for prostate cancer, providing a clear link between the test result and the potential diagnosis of prostate cancer.