Discrepancies in the Detection of PML::RARA Gene Rearrangement by Fluorescent In Situ Hybridization Using Commonly...

Area of Science:

• Hematology
• Molecular Diagnostics
• Cytogenetics

Background:

• Acute Promyelocytic Leukemia (APL) is a life-threatening emergency requiring rapid diagnosis and treatment.
• APL is characterized by the PML::RARA fusion gene, typically detected by FISH.
• Atypical PML::RARA rearrangements can evade detection by standard FISH probes.

Purpose of the Study:

• To evaluate the limitations of commonly used FISH probe sets for detecting atypical PML::RARA rearrangements in APL.
• To highlight the necessity of alternative diagnostic strategies for APL.

Main Methods:

• Analysis of two APL cases with atypical PML::RARA rearrangements.
• Evaluation using two commercially available FISH probe sets (Abbott Molecular and Cytocell).
• Metaphase FISH and qRT-PCR for confirmation of PML::RARA transcript.

Main Results:

• Both cases showed atypical rearrangements with a single fusion signal, leading to differential probe results.
• Metaphase FISH revealed complex rearrangements, including insertions.
• qRT-PCR confirmed the presence of the PML::RARA transcript in both cases.

Conclusions:

• Commonly used PML::RARA FISH probes have limitations in detecting atypical rearrangements.
• Reflex testing with alternative FISH probes and molecular confirmation is essential for accurate APL diagnosis.