or IHC. Next-generation sequencing( NGS) has emerged as a promising molecular diagnostic technique for clinical practice due to its accuracy in detecting most genomic alterations by allowing parallel sequencing in a single assay. 42, 43 NGS is the blanket term used to describe a number of different second- and third- generation sequencing technologies, which are more efficient and show higher throughput than Sanger sequencing, a first-generation sequencing technology. Platforms for NGS from Illumina and Thermo Fisher are used widely. 44 NGS can be applied in the form of large-scale sequencing to detect genetic alterations such as gene mutation and amplification by sequencing the whole genome, exome or transcriptome. By contrast, NGS can also be applied in the form of targeted sequencing to detect and validate genome alterations related to cancer genes by performing deep sequencing on genomic regions of interest. 45
It has been acknowledged that molecular approaches improve the accuracy of ALK fusion detection, by resolving discordant or borderline cases. 46 – 48 However, one of the most valuable advantages of NGS should be attributed to its high negative predictive value compared with FISH testing. Ali et al reported that 35 % of ALKpositive cases detected by NGS were negative in ALK FISH, where only 20 of the 31 ALK-positive cases were concordant for ALK rearrangement and the remaining 11 cases were only NGS-positive. 49 Importantly, the majority of ALK NGS-positive, FISH-negative patients responded to crizotinib,
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