Tumor marker

A tumor marker is a substance, often a protein, that is produced by cancer cells or by normal cells in response to cancer. These markers can be found in the blood, urine, or tissues. They are used by doctors to help detect certain types of cancer, monitor treatment effectiveness, and check for recurrence. However, elevated levels of tumor markers are not exclusive to cancer and can sometimes occur due to benign conditions. Therefore, tumor markers are tools that complement other diagnostic methods, not definitive tests on their own.