cancer
Diagnosis of Cancer
Tumor markers
When examination findings or imaging test results suggest cancer, measuring blood levels of tumor markers (substances secreted into the bloodstream by certain tumors) may provide additional evidence for or against the diagnosis of cancer. In people who have been diagnosed with certain types of cancer, tumor markers may be useful to monitor the effectiveness of treatment and to detect possible recurrence of the cancer. For some cancers, the level of a tumor marker drops after treatment and increases if the cancer recurs. Some tumor markers cannot be measured in the blood but instead can be found on tumor cells. These markers are found by examining tissue from a biopsy sample. HER2 and EGFR are examples of tumor markers found on tumor cells. 