When a biopsy is taken from a tumor, the tissue must be analyzed for cell abnormalities to determine if it is cancerous and malignant. Analysis also reveals the type of cancer the patient has.
The first type of test uses a process called flow cytometry. Flow cytometry is done in a high-tech machine. The process sorts through the cells from the biopsy and examines them for certain cell markers that are found in the membranes of cells. These markers, called clusters of differentiation (CD), identify certain types of cancer cells.
The second test examines the DNA of biopsied cells. Laboratory technicians examine DNA for genetic abnormalities. These abnormalities cause the mutations in cancerous cells, which causes them to grow faster than normal, healthy cells, thus creating a tumor. Identification of these abnormalities helps classify cancer.
Once the biopsied tissue is examined using both of these techniques, the doctor can identify the type of cancer a patient has and then perform the necessary tests to stage the disease.
These tests are also useful in determining the type of treatment to give a patient. Some cell markers bind with antibodies – "tags" that mark the cell for removal by the immune system – so immunotherapy can be used. For more information on this type of treatment, please see the article titled Monoclonal Antibody Therapy.