Your doctor can usually determine that you have non-Hodgkin lymphoma by using a microscope to look at the lymphoma tissue taken from your biopsy. Some people need more than one test to tell which type of lymphocyte, B cell or T cell, is affected.
Your doctor can diagnose lymphoma with a biopsy. But you may need other lab tests to confirm the diagnosis, identify the specific type of lymphoma, and show how rapidly the lymphoma is growing. This information helps determine your treatment plan and gives a sense of your prognosis.
Here are some of the tests you may need:
Cytogenetic analysis. This test is done on a biopsy sample or a bone marrow sample obtained from a bone marrow aspiration. (For a bone marrow aspiration, your doctor takes marrow from your hip bone. The skin over the injection site on the hip will be numbed for this procedure.) The cells are then grown in a laboratory. After about three weeks, a pathologist looks under a microscope at a cell's chromosomes. These are the pieces of DNA that control cell growth. The DNA changes related to lymphoma are not inherited. They usually occur after birth. With some types of lymphoma, chromosomes may exchange DNA. For instance, part of chromosome 1 is on part of chromosome 2 and vice versa. This is called translocation. Or there may be the wrong number of total chromosomes. A chromosome can be deleted, or one can be added.
Molecular genetic tests. These tests may also be used to look for chromosome changes. They usually take less time than cytogenetic tests, so many doctors now prefer to use them. One example is fluorescent in situ hybridization (FISH). This test uses special fluorescent dyes that only attach to specific parts of chromosomes. FISH can find most chromosome changes (such as translocations) that can be seen with standard cytogenetic tests, as well as some changes too small to be seen with usual cytogenetic testing. It can be used on biopsy or bone marrow samples.
Polymerase chain reaction. This is a very sensitive DNA test that can also find some chromosome changes too small to be seen under a microscope, even if there are very few lymphoma cells in a sample.
Immunohistochemistry. This test can help identify the different types of non-Hodgkin lymphoma. For this test, your doctor treats part of the biopsy sample with special antibodies that attach to the cell surface. These antibodies cause color changes seen under a microscope.
Flow cytometry. This is another test that can help tell the type of non-Hodgkin lymphoma. It looks at more cells than immunohistochemistry. Your doctor uses fluorescent antibodies on your biopsy sample and then passes them in front of a laser beam. The laser causes the cells to give off light of different colors, which can be detected with a special machine.