Relevance of EGFR mutation with micropapillary pattern according to the novel IASLC/ATS/ERS lung adenocarcinoma classification and correlation with prognosis in Chinese patients

Abstract

BackgroundA new histological classification by the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) for lung adenocarcinoma (LAC) was proposed recently, in which a micropapillary pattern (MPP) was described. ObjectivesThis study aimed to evaluate the clinicopathological characteristics of LAC with MPP (LAC-MPP) and to investigate the correlation between LAC-MPP and epidermal growth factor receptor (EGFR) mutation status with the prognosis in Chinese patients. Patients and methodsFrom May 2007 and February 2012, two hundred and forty-eight patients underwent resection and pathologically confirmed LAC. We classified all cases histologically according to the IASLC/ATS/ERS classification; an MPP ratio ≥5% was considered MPP-positive. Used Pearson's chi-square test to evaluate the relationships between EGFR mutation status and MPP status with patient clinicopathological characteristics. ResultsThere were MPP-positive tumors (MPP ratio ≥5%) in 31.9% of cases (79/248); the MPP ratio correlated with TNM stage (p=0.001) and lymph node metastasis (p=0.03). EGFR mutation (EGFR-mut) was detected in 87 cases (34.3%); 161 cases had wild-type EGFR (EGFR-wt). EGFR mutation was present in 65% of the MPP-positive subtype. Patients with EGFR-mut tumors had significantly longer overall survival (OS) (p=0.002). OS was also significantly longer in MPP-negative EGFR-mut or EGFR-wt patients (p<0.001). ConclusionThese findings indicate that EGFR-mut tumors are likelier to be MPP-positive subtypes and that MPP may be a novel potential pathological marker of poor prognosis in Chinese LAC patients.