[Clinicopathological Characteristics of ROS1-positive 
Non-small Cell Lung Cancer Based on Next-generation Sequencing]

C-ROS proto-oncogene 1 receptor tyrosine kinase (ROS1) gene fusion-positive non-small cell lung cancer (NSCLC) is a high-risk subtype of lung cancer, and the accurate identification of this specific subtype is critically important. This study systematically analyzes the concordance between the results of next-generation sequencing (NGS), immunohistochemistry (IHC), and fluorescence in situ hybridization (FISH) to validate the clinical value of IHC as an initial screening tool for ROS1 fusions.

Patients with NSCLC diagnosed at Cancer Hospital, Chinese Academy of Medical Sciences between November 1, 2020 and November 30, 2022 were enrolled. All cases were tested for ROS1 gene fusion via NGS, re-examined with hematoxylin-eosin (HE) staining, and ROS1 protein expression and gene breakage were detected using IHC and FISH. The results of the three detection methods and their correlation with clinicopathological characteristics were compared.

22 were detected as ROS1 fusion-positive among 770 NSCLC cases. Histologically, all were lung adenocarcinoma, predominantly poorly differentiated. The main growth patterns included solid, acinar, and papillary types. IHC detection showed positive expression of ROS1 protein in all 22 cases, including 14 cases (63.6%) with strong diffuse positivity, resulting in a positive concordance rate of 100.0%. FISH detection revealed a typical isolated signal pattern in 16 cases, with a positive concordance rate of 72.7%. The overall concordance rate among NGS, IHC, and FISH was 72.7%.

ROS1 fusion-positive NSCLC exhibits characteristic clinicopathological features. In ROS1 fusion-positive cases confirmed by NGS, IHC serves as a highly sensitive tool with 100.0% sensitivity, suggesting its potential as an initial screening method, but its specificity still needs further verification. NGS testing is recommended as a priority in cases with strong ROS1 IHC positivity. When strong IHC positivity is observed alongside atypical FISH signals, NGS becomes a key technique for confirmation and precise identification of fusion partners and breakpoints. An integrated diagnostic strategy combining histomorphological evaluation, IHC preliminary screening, and NGS validation facilitates accurate diagnosis of ROS1-positive lung cancer, thereby guiding clinical targeted therapy implementation.