Mutation profile and programmed death ligand 1 status of patients with non-small cell lung cancer diagnosed with "adenocarcinoma" and "non-small cell carcinoma favor adenocarcinoma"

Background: The terminology for lung cancer diagnosis in small biopsies was adopted in the 2015 World Health Organization classification. If non-small cell lung cancer (NSCLC) has no clear adenocarcinoma (AD) or squamous cell carcinoma morphology, the tumor is further classified based on mucin or immunohistochemical staining as NSCLC favor AD (NFAD), NSCLC favor squamous cell carcinoma, or NSCLC not otherwise specified. Since this new term was defined, the difference between AD and NFAD has not yet been fully explored. This study aimed to examine the differences in clinical background, gene alteration frequency, and programmed death ligand 1 (PD-L1) expression.Methods: We included patients diagnosed with AD or NFAD with small samples, and who underwent testing with the Oncomine Dx target test between August 2019 and April 2023 in Kanagawa Cancer Center.Results: This study comprised 268 patients. A total of 96 patients underwent surgery after AD or NFAD diagnosis. The clinical stage was more advanced and pathological N0 was lower in NFAD than in AD. The pathology of the surgical specimens revealed that solid predominant AD was significantly more common in NFAD than in AD (p < 0.001). In both AD and NFAD, EGFR mutation was the most frequent gene alteration, followed by KRAS mutation. The frequency of EGFR mutations was significantly higher in AD than in NFAD. PD-L1 expression was significantly higher in NFAD than in AD (p < 0.001).Conclusion: This study shows a clear difference between AD and NFAD in terms of cancer progression, pathological features of the main tumor, genetic characteristics, and PD-L1 expression.