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. 2019 Feb;12(2):389-395.
doi: 10.1016/j.tranon.2018.11.006. Epub 2018 Dec 4.

Discordance between FISH, IHC, and NGS Analysis of ALK Status in Advanced Non-Small Cell Lung Cancer (NSCLC): a Brief Report of 7 Cases

Anna Scattone  1 , Annamaria Catino  2 , Laura Schirosi  3 , Lucia Caldarola  4 , Stefania Tommasi  5 , Rosanna Lacalamita  5 , Elisabetta Sara Montagna  2 , Domenico Galetta  2 , Gabriella Serio  6 , Francesco Alfredo Zito  1 , Anita Mangia  7
Affiliations

Discordance between FISH, IHC, and NGS Analysis of ALK Status in Advanced Non-Small Cell Lung Cancer (NSCLC): a Brief Report of 7 Cases

Anna Scattone et al. Transl Oncol. 2019 Feb.

Abstract

Background: Anaplastic lymphoma kinase (ALK) rearrangement represents a landmark in the targeted therapy of non-small cell lung cancer (NSCLC). Immunohistochemistry (IHC) is a sensitive and specific method to detect ALK protein expression, possibly an alternative to fluorescence in situ hybridization (FISH). In this study, the concordance of FISH and IHC to determine ALK status was evaluated, particularly focusing on discordant cases.

Materials and methods: ALK status was tested by FISH and the IHC validated method (Ventana ALK (D5F3) CDx Assay) in 95 NSCLCs. Discordant cases were analyzed also by next-generation sequencing (NGS). The response to crizotinib of treated patients was recorded.

Results: Seven (7.3%) discordant cases were ALK FISH positive and IHC negative. They showed coexistent split signals pattern, with mean percentage of 15.4%, and 5' deletions pattern, with mean percentage 31.7%. Two cases had also gene amplification pattern. In three cases (42.8 %), the polysomy was observed. The NGS assay confirmed IHC results. In these patients, the treatment with crizotinib was ineffective.

Conclusions: In our discordant cases, a coexistent complex pattern (deleted, split, and amplified/polysomic) of ALK gene was observed by FISH analysis. These complex rearranged cases were not detectable by IHC, and it could be speculated that more complex biological mechanisms could modulate protein expression. These data highlight the role of IHC and underscore the complexity of the genetic pattern of ALK. It could be crucial to consider these findings in order to best select patients for anti-ALK treatment in daily clinical practice.

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Figures

Figure 1
Figure 1
Representative images of one sample with discordant ALK IHC and FISH status. (A) Hematoxylin-eosin staining of a sample with adenocarcinoma histotype (Magnification ×20). (B) ALK IHC negative status (magnification ×20). (C) ALK FISH-positive case with typical split signals. (magnification ×60). (D) ALK FISH-positive case with 5' deletion pattern (magnification ×100). (E) ALK FISH-positive case with gene amplification pattern (magnification ×100). (F) Polysomy pattern of chromosome 2 (magnification ×100).
See this image and copyright information in PMC

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