OVERVIEW
Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasm, predominantly affecting granulocytes, whereas Philadelphia positive acute lymphoblastic leukemia (Ph+ve ALL) is a B-cell lymphoproliferative neoplasm. Both are most often characterized by the reciprocal translocation of chromosomes 9 and 22 – t(9;22)(q34.1;q11.2). The resulting derivative 22 chromosome (der22) is colloquially described as the Philadelphia chromosome (Figure 1). Both complex and cryptic rearrangements involving BCR and ABL1 have also been described.
Figure 1: The reciprocal translocation of chromosomes 9 and 22 resulting in the Philadelphia chromosome
INDICATION
BCR::ABL1 FISH is offered for patients suspected of being affected with the following:
- Chronic Myeloid Leukemia
- Ph+ve Acute Lymphoblastic Leukemia
- Ph+ve Acute Myeloid Leukemia
REFERRAL
Any BC licensed Medical Oncologist, Hematologist, or Pathologist
TEST REQUIREMENTS
- Completed CGL Myeloid Testing requisition form
- One of the following specimens (see our Specimens Guidelines, Cytogenetics test type):
- 4mL peripheral blood collected in sodium heparin tubes (green top)
- 2×1.0 mL of marrow aspirate in 9mL media (RPMI 1640, 3.8% FBS, antibiotics)
- Also accepted, but not preferred: Bone marrow biopsy in 9mL media (RPMI 1640, 3.8% FBS, antibiotics)
Contact our laboratory for ready prepared media tubes.
TRANSPORT
See our Guidelines for Specimens and Transport
METHOD
The submitted specimen is harvested into a methanol-acetic acid (MAA) fixed cell pellet. The pellet is used to perform FISH analysis on interphase nuclei, as well as metaphases if available. FISH is performed using the BCR/ABL dual-fusion probe (Vysis).
Adapted from: https://www.molecular.abbott/int/en/vysis-fish-chromosome-search
 | Normal Hybridization: Result of the hybridization of the LSI BCR/ABL Dual Color, Dual Fusion Translocation Probe as observed in a normal interphase cell. Adapted from: https://www.molecular.abbott/int/en/vysis-fish-chromosome-search |
 | Abnormal Hybridization: Result of the hybridization of the LSI BCR/ABL Dual Color, Dual Fusion Translocation Probe as observed in an interphase cell harbouring a balance reciprocal translocation involving BCR and ABL1. Adapted from: https://www.molecular.abbott/int/en/vysis-fish-chromosome-search |
CLINICAL UTILITY
Up to 99% of CML cases will have a translocation involving BCR and ABL1 visible by FISH, aiding in the diagnosis of CML.
TURN-AROUND TIME
Final results are reported within seven days from receipt of specimen and completed requisition form. Failed analyses may be repeated at the discretion of the Laboratory Geneticist or Director, should sufficient sample be available for repeat analysis.