NCCN Guidelines for Patients® | Myeloproliferative Neoplasms

18 NCCN Guidelines for Patients ® : Myeloproliferative Neoplasms, 2018 2 Testing for MPN Genetic tests Genetic tests Genetic tests assess for abnormal changes in genes and chromosomes. These tests are used for diagnosis and treatment planning. The genetic tests for MPN are described next. BCR-ABL1 CML ( c hronic m yeloid l eukemia) is a type of MPN. It is the only cancer that has the BCR-ABL1 fusion gene. Normal blood cells do not have this gene. It is formed when parts of chromosomes 9 and 22 break off and switch with each other. Testing for BCR-ABL1 is advised to rule out CML. One of the following two tests can be used. QPCR QPCR ( q uantitative reverse transcriptase- p olymerase c hain r eaction) measures the number of cells that have the BCR-ABL1 fusion gene. Either a bone marrow or blood sample can be used. QPCR is very sensitive. It can find one CML cell among more than 100,000 normal cells. FISH FISH ( f luorescence i n s itu h ybridization) uses special color dyes—called probes. The probes attach to the BCR gene and the ABL gene. The BCR- ABL1 fusion gene is detected when the colors of the probes overlap. This test can be performed on either a bone marrow or blood sample. Bone marrow cytogenetics Cytogenetics is the study of chromosomes. For MPNs, bone marrow cells should be tested. Blood may be used if a marrow sample can’t be obtained. However, finding an abnormal change is less likely when using blood. Doctors use cytogenetics for a few reasons. It may be used to assess clonality but molecular testing is often used instead. MPNs are a clonal disease. This means all the cancer cells came from the same parent cell. In the late phases of MPNs, it is common for cells to have abnormal chromosomes. There are many types of chromosome defects. A part of or the entire chromosome may be missing. There may be an extra part in a chromosome. Parts of chromosomes may have switched places with each other. The outlook (prognosis) is usually worse if many abnormal changes are present. Cytogenetics are also used to assess treatment results. Treatment is working well if tests show the defects are no longer present. Defects reappear when treatment stops working. More information on checking treatment results is in Parts 3 through 5. Karyotype ± FISH Cytogenetics for MPN is done with a karyotype. FISH may be used, too. A karyotype is a picture of the chromosomes in cells. See Figure 6 . A chemical will be added to the marrow sample to start cell growth. Then, an expert will study the cells with a microscope. A “complex karyotype” may be present. A complex karyotype is when there are 3 or more unrelated defects in chromosomes that occur in more than one cell. Molecular testing Molecular testing includes tests of genes or their products (proteins). There are three common gene mutations among MPNs as well as others. Testing for these mutations is needed for diagnosis. The outlook of the disease also depends on which mutations are present. A blood sample may be used for testing. Molecular testing for MPN includes the following: JAK2 mutations The most common mutation among MPNs is the JAK2 V617F mutation. It occurs in chromosome 9 in a part of the JAK2 gene called exon 14. It is present in almost everyone with PV. It is also present in over