Aims Diagnostic tumour samples are mandatory for morphologic and molecular diagnosis of non-small cell lung cancer (NSCLC) to establish the best therapeutic approach. In the presence of small tumour tissue sample, the pathologist needs to make responsible choices to achieve a correct diagnosis and save material for subsequent molecular evaluations. Nevertheless, in some instances, the diagnostic process can lead to tissue depletion. The automated Idylla epidermal growth factor receptor (EGFR) mutation test has been developed to rapidly process formalin-fixed paraffin-embedded (FFPE) pathologic material, without previous DNA extraction. This study aimed to test whether this platform is suitable for the reuse of H&E, immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH) diagnostic slides.
Methods A training set of 19 FFPE tissues with known EGFR status was revaluated on H&E slides. Fourteen of them were also tested using IHC and FISH treated specimens. An additional series of 25 H&E, IHC or FISH slides of NSCLC cases tested for EGFR mutation at an external institution was blindly assessed as a validation cohort.
Results Combining the two sets, 32 of 32 classical ex19dels and p.L858R were correctly identified. Three uncommon mutations (p.G719X, p.L861Q and ex20ins) were also detected. Four discrepancies were related to rare ex19del/ins not included in the Idylla list of detectable mutations. Two p.T790M variants were missed on one FFPE and two H&E slides but were detected using IHC and FISH sections from the same FFPE blocks.
Conclusions The Idylla EGFR mutation test is highly reliable using differently treated tumour specimens and should be validated in larger studies.
- lung neoplasms
- medical oncology
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Handling editor Runjan Chetty.
Correction notice This article has been corrected since it was published Online First. The affiliations of all the authors have been corrected.
Contributors JN, PG, GM and LRG helped in conception, design, tissue validation and writing. LAM, ADL and MB performed conception, data acquisition, interpretation and writing. AR was responsible for critical review of data and writing. AL helped in conception, design, tissue validation, data acquisition, interpretation and writing.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Molecular data pertaining to deidentified tumour specimens are available from firstname.lastname@example.org.
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