Abstract: Objective：To examine the prevalence of anaplastic lymphoma kinase (ALK) fusion gene in Chinese patients with non-small cell lung cancer (NSCLC). Methods: In this study, 95 patients with NSCLC and corresponding clinical information and formalin-fixed paraffin-embedded (FFPE) tissue blocks were included. Hematoxylin & eosin (HE) staining, conventional ALK immunochemistry (IHC) staining and intercalated antibody-enhanced polymer (iAEP) IHC staining, and dual-color split fluorescence in situ hybridization (FISH) for ALK fusion gene were performed. Results: Eight ALK-positive cases were detected using anti-ALK immunohistochemistry with the iAEP method, and FISH analyses revealed 4 patients of them who harbored the ALK fusion gene (4.2%, 4/95), including 2 cases of female patients with solid signet-ring cell adenocarcinoma and 2 cases of male patients with adenosquamous carcinoma. The positive cases were all non-smokers without EGFR/KRAS mutations. Furthermore, the positive cases all survived, and the overall postsurgery survival time of 2 cases was more than 5 years. Conclusion: ALK IHC with the iAEP method is better than conventional ALK IHC, and the percentage of the positive cells is more important than that of the intensity. ALK translocations were infrequent in the entire NSCLC patient population (<5%) with better prognosis.

Key words: Carcinoma, non-small-cell lung, Anaplastic lymphoma kinase, Gene fusion, Immunohistochemistry, In situ hybridization, fluorescence