NCCN Guidelines for Patients® | Myelodysplastic Syndromes
20 NCCN Guidelines for Patients ® : Myelodysplastic Syndromes, 2018 2 Testing for MDS Genetic tests There are many types of chromosome defects. Part of a chromosome, or a whole chromosome, may be missing. Or, there may be an extra copy of a chromosome. Doctors use symbols and shortened terms to describe the different types of chromosome changes. A missing chromosome or missing part of a chromosome is noted by a minus sign (-) or the word “del” for deletion. An extra copy of a chromosome is noted by a plus sign (+). For example: -7 and del(7) both mean that a copy of chromosome 7 is missing. del(7q) and 7q- both mean that the “q” part (long arm) of chromosome 7 is missing. The “p” part is the short arm of the chromosome. +7 means that there is an extra copy of chromosome 7. It is common for MDS cells to have abnormal chromosomes. About half of patients with MDS have one or more chromosome defects. In MDS cells, defects are commonly found in chromosomes 5, 7, 8, and 20. The type and number of chromosome changes helps doctors assess the likely outcome (prognosis) for your MDS. This information can also help guide treatment options. FISH Sometimes the bone marrow cells don’t grow well. If this happens, FISH, which uses special dyes to find specific changes in a cell’s genes and chromosomes can be used. FISH testing can be done on a sample of blood or bone marrow. This test detects specific gene or chromosome changes that are common and known to affect outcome in patients with MDS. FISH testing can be used in addition to karyotyping to identify specific changes that are known to be common in MDS. Knowing if the MDS cells have certain gene changes can help to guide treatment choices. FISH is not used to confirm MDS and may not be needed for all patients. Molecular testing Molecular testing is more sensitive than either karyotype or FISH. With molecular testing you can find small changes (mutations) in genes that are known to have an effect on cancer treatment or outcomes. Many times, patients with a normal karyotype (50% of those with MDS) will have detectable changes at a molecular level. Molecular testing can be done on a sample of blood or bone marrow removed from your body. Molecular testing may be done in some patients with MDS to look for the following gene changes.