Related Experiment Video
Updated: Oct 29, 2025
Author Spotlight: FISH as a Tool for Precise Gene Amplification Assessment in Cancer Specimens
Published on: July 12, 2024
Analytical Accuracy of RET Fusion Detection by Break-Apart Fluorescence In Situ Hybridization
Jessica A Baker1, Anthony N Sireci2, Narasimha Marella2
1From Diagnostic and Experimental Pathology (Baker, Cannon, Holzer, Reising, Cook, Schade, Oakley III).
Context.—:
RET gene fusions are oncogenic drivers in nonsmall cell lung cancer and nonmedullary thyroid cancer. Selpercatinib (RETEVMO), a targeted inhibitor of RET, was approved by the US Food and Drug Administration for the treatment of RET fusion-positive nonsmall cell lung cancer and nonmedullary thyroid cancer emphasizing the need for rapid and accurate diagnosis of RET fusions. Fluorescence in situ hybridization (FISH) has been used to detect gene rearrangements, but its performance detecting RET rearrangements is understudied.
Objective.—:
To validate and describe the performance of Abbott Molecular RET break-apart FISH probes for detecting RET rearrangements.
Design.—:
A training set with RET fusion-positive (13) and RET fusion-negative nonsmall cell lung cancer and nonmedullary thyroid cancer samples (12) was used to establish criteria for FISH scoring. The scoring criteria was then applied to a larger validation set of samples (96).
Results.—:
A cutoff of 19% or more positive nuclei by FISH was established in the training set and determined by the mean ±3 SD. The validation set was tested using Abbott Molecular RET break-apart FISH compared with sequencing. With this cutoff, a sensitivity of 86% (12 of 14) and specificity of 99% (81 of 82) was achieved. Bootstrapping showed sensitivity could be optimized by using a greater than 13% cutoff with indeterminate samples of 13% to 18% abnormal nuclei requiring confirmation by an orthogonal method. Using this 3-tier scoring system sensitivity increased to 100% (14 of 14) and specificity was 96% (79 of 82).
Conclusions.—:
Abbott Molecular break-apart FISH probes can be used to detect RET fusions. Laboratories can optimize cutoffs and/or testing algorithms to maximize sensitivity and specificity to ensure appropriate patients receive effective, timely therapy.
Insights
Abbott Molecular RET break-apart FISH probes accurately detect RET fusions in cancer. Optimizing scoring criteria enhances sensitivity and specificity for timely patient therapy.
Area of Science:
- Oncology
- Molecular Diagnostics
- Genetics
Background:
- RET gene fusions are key drivers in non-small cell lung and thyroid cancers.
- Selpercatinib targets RET, necessitating precise RET fusion detection.
- Fluorescence in situ hybridization (FISH) is a diagnostic tool with understudied performance for RET rearrangements.
Purpose of the Study:
- To validate and characterize Abbott Molecular RET break-apart FISH probes.
- To assess the diagnostic accuracy of FISH for RET rearrangements.
Main Methods:
- A training set (25 samples) established FISH scoring criteria for RET fusions.
- A validation set (96 samples) tested probe performance against sequencing.
- A 3-tier scoring system was evaluated to optimize sensitivity and specificity.
Main Results:
- An initial cutoff of ≥19% positive nuclei yielded 86% sensitivity and 99% specificity.
- A revised 3-tier system (≥13% positive nuclei) improved sensitivity to 100% and specificity to 96%.
- Abbott Molecular RET break-apart FISH probes demonstrated high accuracy in detecting RET fusions.
Conclusions:
- Abbott Molecular break-apart FISH probes are effective for detecting RET fusions.
- Laboratories can optimize cutoffs and algorithms to maximize diagnostic accuracy.
- Accurate RET fusion detection ensures timely and effective patient treatment.
