Genomic Heterogeneity Of Multi-nodular Lesions With High Incidence Of Lung Adenocarcinoma In Yunnan

[Objective]Lung carcinoma presenting with multiple nodules are detected with increasing frequency,distinguishing synchronous primary lung adenocarcinomas from intrapulmonary metastasis is essential for optimal patient management.This study intends to use the method of whole exome sequencing to explore the clonal origin relationship between simultaneous multinodular lung adenocarcinoma lesions from the perspective of molecular genetics.[Methods]Select 10 patients with simultaneous multinodular lung adenocarcinoma who were treated at the Third Affiliated Hospital of Kunming Medical University from November 2019 to July 2020 were selected.Collect surgically resected multi-nodular tumor tissue samples and their own distal normal lung tissue samples,and perform whole-exome sequencing.Through bioinformatics analysis,the genomic mutation profile results of multiple nodular lesions were obtained.Comprehensive clinical pathological data and molecular genetic heterogeneity between lesions to distinguish multiple nodules from "multiple primary lung cancer" or "intrapulmonary metastasis".[Results]1、Clinicopathological characteristics of lung adenocarcinoma with multiple nodulesIn the 10 patients with simultaneous multinodular lung adenocarcinoma,preoperative chest CT indicated that 3 cases were located in the same lobe,6 cases were located in different ipsilateral lobes,and 1 case was located in bilateral lobes;all of the multi-nodular histopathological types were confirmed to be lung adenocarcinoma;according to the Martini-Melamed standard considering multiple primary lung cancer 7 cases,pulmonary metastatic carcinoma in 3 cases;The eighth edition of lung cancer TNM:I A stage 5 cases,Ⅱ B stage 3 cases,ⅢA stage 1 cases,ⅢB stage 1 cases.2、Whole exome sequencing to obtain somatic mutation dataTwenty-one tumor samples from 10 simultaneous multinodular lung adenocarcinomas were sent for whole exome sequencing.Average sequencing depth was 291X,and the coverage of the target region reached 99.21%.A total of 5756 non-synonymous mutations were detected in the coding area,including 5423 missense mutations and 333 nonsense mutations.All the lesions of multi-nodular tumor showed different somatic mutation characteristics,and the difference of somatic mutation spectrum in patient 2 was statistically significant(P value<0.01).The base substitutions in the mutation spectrum of smokers are mainly C>A,and mutation Signature B is similar to Signature 4 in the COSMIC database,suggesting that tobacco exposure is involved in the process of carcinogenesis.3、Differentiation of multinodular lesions by heterogeneity of somatic mutation spectrumWhole exon sequencing was used to obtain somatic variation results of 21 tumor tissue samples.Similarity analysis of somatic mutation spectrum,high-frequency mutation gene analysis and phylogenetic evolution analysis suggested that the vast majority of lesions among multiple pulmonary nodules might be multiple primary tumors.Except Pa4T2 and Pa4T3 lesions,the average similarity of somatic mutation patterns was about 0.59%(0%-1.85%).The phylogenetic tree analysis among the lesions of the same patient showed independent branches and did not support the same clonal origin relationship.The frequency of EGFR mutations is high in the analysis of somatic high frequency mutations.EGFR mutations were found in all lesions of patient 4.Pa4T2 and Pa4T3 have the same EGFR rare mutations,EGFR exon18:c.G2155T p.G719C,consider intrapulmonary metastasis.In addition,three patients were clinically diagnosed as intrapulmonary metastasis.According to the results of the genome somatic mutation heterogeneity in this study,metastasis has been ruled out.The multinodular lesions in the lung were corrected to multiple primary lung adenocarcinomas,and they were re-staged.[Conclusions]1、There are significant differences in the mutation spectrum of multi-nodular tumors of lung cancer in Yunnan,genetic heterogeneity of multi-nodular lung adenocarcinoma suggests its independent clonal origin.For example,rare mutations in lung cancer driver genes have more clinical significance in identifying the nature of multiple nodules.2、When multiple primary lung cancers are considered for multi-nodular tumor lesions with the same histopathology,molecular genetic criteria are recommended as an important basis for identification.