Korean J Clin Pathol.  2001 Aug;21(4):253-259.

Utility of RARa Fluorescence In Situ Hybridization for Follow-up in Acute Promyelocytic Leukemia: Comparison with PML/RARa Fluorescence In Situ Hybridization

  • 1Department of Clinical Pathology, Seoul National University College of Medicine, Seoul, Korea.
  • 2Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.


The most noted rearrangement identified in acute promyelocytic leukemia (APL) involves the PML and RARa genes, which results in the formation of the PML/RARa gene fusion. In the fluorescence in situ hybridization (FISH) for PML/RARa, the two signals may coincidentally overlap in normal nuclei. We investigated whether a new RARa rearrangement probe could discriminate the false-positive fusion signal of the PML/RARa translocation probe.
A total of 51 cases, which showed the results from 1% to the borderline level by PML/ RARa FISH, were re-tested with the RARa rearrangement probe. Also, we compared the RARa FISH with the PML/RARa FISH on 16 patients with newly diagnosed APL and performed the RARa FISH on 20 bone marrow specimens without hematologic malignancies in order to set up the cut-off value.
The cut-off for the RARa FISH was determined as 1.02%. For patients with newly diagnosed APL, the PML/RARa FISH showed positive signals in 95.3+/-6.5% of the cells and RARa FISH showed positive signals in 97.0+/-7.0% (r=0.83). Of a total of 41 cases consisting of hematological disorders other than APL, five cases showed results equal to or greater than 5% with PML/RARa FISH and one case showed a positive result with RARa FISH. Of 10 follow-up APL cases, seven cases showed results equal to or greater than 5% with the PML/RARa FISH and four cases showed positive results with the RARa FISH.
The cut-off value for the RARa FISH is 1.02% and we consider RARa FISH as the proper method for follow-up of APL.


RARa FISH; RARa rearrangement probe; PML/RARa FISH; acute promyelocytic leukemia

MeSH Terms

Bone Marrow
Follow-Up Studies*
Gene Fusion
Hematologic Neoplasms
In Situ Hybridization*
Leukemia, Promyelocytic, Acute*
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