20 NCCN Guidelines for Patients ® : Multiple Myeloma, 2019 2 Testing for myeloma Tissue tests Tissue biopsy If you have a solitary plasmacytoma, a tissue biopsy may be done to remove a sample of the mass for testing. The sample is often removed with a needle. This can be done with an FNA ( f ine- n eedle a spiration) biopsy or with a core needle biopsy. An FNA biopsy uses a very thin needle to remove a small sample from the mass. A core needle biopsy uses a larger needle to collect a larger sample of tissue. For a tissue biopsy, an imaging test may be used to guide the needle through the skin and into the mass. Lab tests After the tissue samples are collected, they will be sent to a lab for testing. A pathologist will view the samples under a microscope to look for myeloma cells. The pathologist may also perform other tests on the samples. It often takes several days before the test results are known. The lab tests that may be performed on the tissue samples are described next. Flow cytometry This is a test that measures the amount of myeloma cells in the bone marrow. This test can tell the difference between normal plasma cells and abnormal plasma cells (myeloma cells). Immunohistochemistry This test is performed on the bone marrow biopsy sample. It is used to measure the number of myeloma cells in the bone marrow. Genetic tests Genetic tests are used to check for abnormal chromosomes and genes. Different types of tests are done with the cells. First, bone marrow cells are grown to make the cells divide. Next, the dividing cells can be examined. Cytogenetic testing uses a microscope to examine the chromosomes inside cells. This type of test is used to look for abnormal changes in the chromosomes of the myeloma cells. For myeloma, this is done on a sample of bone marrow. While examining the cells, a pathologist will also look at a “map” of the chromosomes under a microscope. This is called karyotyping . It will show if there are any abnormal changes in the size, shape, structure, or number of chromosomes. Myeloma cells can also be examined with a test called FISH. FISH uses probes that attach to certain parts of the chromosomes known to be affected in myeloma. FISH testing is very important to determine whether a patient’s myeloma can be considered standard risk or high risk. The newest testing, called gene expression , looks for certain genes that may be turned on or turned off in myeloma cells. This is not routinely performed. Plasma cell proliferation This test shows what percentage of the myeloma cells are dividing. A larger number of cells dividing is a sign that the cancer will grow fast. Light chain amyloidosis Amyloid is a rare protein found in people with abnormal plasma cells that make abnormally folded light chains. Amyloid can collect and build up in tissues and organs throughout the body. The buildup of amyloid, called amyloidosis , can damage organs such as the heart and kidneys. Tests for light chain amyloidosis can be done on a sample of bone marrow, the fat pad—fat from just under the skin of the belly, or other biopsy of an organ with amyloid deposits.