particular disease process, and they are used in oncology to help detect the presence of cancer. An elevated level of a tumor marker can indicate cancer; however, there can also be other causes of the elevation (false positive values).Tumor markers can be produced directly by the tumor or by non-tumor cells as a response to the presence of a tumor. Although mammography, ultrasonography, computed tomography, magnetic resonance imaging scans, and tumor marker assays help in the staging and treatment of the cancer, they are usually not definitive diagnostic tests. The diagnosis is mostly confirmed by biopsy. umor markers may be used for the following purposes:

Screening for common cancers on a population basis. Broad screening for all or most types of cancer was originally suggested but has since been shown not to be a realistic goal. Screening for specific cancer types or locations requires a level of specificity and sensitivity that has so far only been reached by Example: elevated prostate specific antigen suggests that is used in some countries to screen for prostate cancer.Monitoring of cancer survivors after treatment, detection of recurrent disease. Example: elevated AFP in a child previously treated for teratoma suggests relapse with endodermal sinus tumor. Diagnosis of specific tumor types, particularly in certain brain tumors and other instances where biopsy is not feasible. Confirmation of diagnosis to verify the characteristics such as size and aggressiveness of a tumor and thereby to help in the evaluation of a suitable treatment schedule.