Morphological and molecular approach to synchronous non-small cell lung carcinomas: impact on staging.

Distinction between multiple primary cancers and intrapulmonary metastases in patients with synchronous multifocal lung cancer can be challenging. Histological and genotypic assessment of multifocal lung tumors have been suggested to influence the staging. The aim of this study was to determine the role of morphology and genotype in staging of surgically treated multifocal non-small cell lung carcinoma. Synchronous lung cancers from 60 patients (42 with adenocarcinoma and 18 with squamous cell carcinoma), clinically considered to represent intrapulmonary metastases, were histologically subtyped according to the 2015 World Health Organization classification of lung tumors and subjected to genotypic analysis (KRAS, EGFR, BRAF, PIK3CA, ALK, MET and ROS1 in adenocarcinoma and PIK3CA and p16 in squamous cell carcinoma). Concordance between clinical criteria and histological subtyping was identified in about 50% of cases (P<0.0001). Genotypically, 44% of adenocarcinomas and 60% of squamous cell carcinomas with identified molecular alterations were considered to be intrapulmonary metastases. Concordance between histological and molecular staging was observed in 89% of adenocarcinomas and 56% of squamous cell carcinomas. Univariate survival analyses failed to demonstrate significant differences in overall or cancer-specific survival in patients with adenocarcinoma and squamous cell carcinomas restaged according to histology and/or molecular profile. Lymph node metastases (N1/N2 vs N0) (P=0.03) and age >65 years (P=0.05) were associated with shorter overall survival. In addition, squamous cell carcinomas with p16 deletion showed shorter overall survival when compared with squamous cell carcinomas without p16 deletion (P=0.05). No correlation between other molecular alterations, clinico-pathological characteristics and prognosis was found. Our study demonstrates that a comprehensive genotypic and morphological assessment of surgically treated multifocal lung cancers is feasible but not sufficient to establish their clonal relationship and prognosis.