NOTE: Our laboratory offers multiple testing options for APL. Please see our APL overview page.
Acute promyelocytic leukemia (APL) is a clonal myeloproliferative neoplasm, wherein abnormal promyelocytes predominate. APL is most often characterized by the reciprocal translocation of chromosomes 15 and 17 – t(15;17)(q24;q12) (Figure 1). Rarely, RARA may combine with another fusion partner.
Testing is offered for all patients suspected of being affected with acute promyelocytic leukemia
Any BC licensed Medical Oncologist, Hematologist, or Pathologist
- Completed CGL Myeloid Testing requisition form
- One of the following specimens (please see our Specimen Guidelines, RNA Molecular 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)
- Accepted, but not preferred: Bone marrow biopsy in 9mL media (RPMI 1640, 3.8% FBS, antibiotics)
- Contact CGL for ready prepared media tubes.
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 PML-RARA dual-fusion probe (Vysis).
|Normal Hybridization: Result of the hybridization of the LSI PML/RARA Dual Color, Dual Fusion Translocation Probe as observed in a normal interphase cell|
|Abnormal Hybridization: Result of the hybridization of the LSI PML/RARA Dual Color, Dual Fusion Translocation Probe as observed in an interphase cell harbouring a reciprocal translocation involving PML and RARA.|
Up to 98% of APL cases will have a translocation involving PML and RARA visible by FISH, aiding in the diagnosis of APL. Karyotype may detect rare RARA fusions that cannot be detected by FISH. Should the index of suspicion remain high following a negative FISH result, follow-up molecular investigations may be warranted.
TURN AROUND TIME
Urgent (STAT) FISH samples have a verbal TAT target of 3-5 days. Final results are reported within fourteen 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.