Association Between the Histological Subtype of Lung Adenocarcinoma, EGFR/KRAS Mutation Status and the ALK Rearrangement According to the Novel IASLC/ATS/ERS Classification

The present study aimed to investigate the association between epidermal growth factor receptor (EGFR)/Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations, anaplastic lymphoma receptor tyrosine kinase (ALK) rearrangements and the morphological characteristics of lung adenocarcinoma (LAC), according to the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) classification in a large group of patients with primary LAC. A total of 200 patients with invasive LAC who had undergone complete resections at the Beijing Chest Hospital (Beijing, China) were randomly selected. The morphology of the samples was reassessed in 5% increments by two pathologists, according to the IASLC/ATS/ERS scheme. EGFR and KRAS mutations were tested by direct DNA sequencing. ALK rearrangements were screened by immunohistochemistry on a Benchmark XT stainer. The data revealed that EGFR and KRAS mutations, and ALK rearrangements were identified in 46.0% (92/200), 9.0% (18/200) and 11.5% (23/200) of the patients, respectively. The EGFR/KRAS mutations and ALK rearrangements were mostly exclusive. However, 1 patient exhibited the coexistence of the EGFR (at exon 20) and KRAS (codon 12) mutations, and another patient exhibited the coexistence of the EGFR mutation (at exon 21) and the ALK gene fusion. EGFR mutations were indicated to be closely associated with the acinar predominant (43/77; 55.8%; P=0.030) and papillary predominant (26/49; 53.1%; P=0.006) subtypes. KRAS mutations were more commonly associated with the solid predominant subtype (9/52; 17.3%; P=0.023) and invasive mucinous LAC (5/10; 50.0%; P=0.004), and less commonly associated with the acinar predominant subtype (1/77; 1.3%; P=0.002). ALK rearrangements more commonly occurred in the solid predominant subtype compared with other subtypes (13/52; 25%; P=0.002), and less commonly occurred in the papillary predominant subtype (1/49; 2.0%; P=0.004). Tumors harboring ALK rearrangements were characterized by signet-ring cell (7/9; 77.8%; P<0.0001) and cribriform (7/12; 58.3%; P<0.0001) patterns. The association between the mutation status and histological subtype in LAC was distinct. The predominant subtype according to the IASLC/ATS/ERS classification provided important information for gene mutations and integrated clinical findings to improve the treatment of LAC patients.