Abstract: OBJECTIVE：Relationships between DNA ploidy abnormality and epidermal growth factor receptor (EGFR) gene mutation in pleural effusion from metastatic lung adenocarcinomas and their effects on prognosis of patients. METHODS：Clinical data of 439 patients with lung adenocarcinomas and with malignant pleural effusions were collected from the Fourth Hospital of Hebei Medical University from 2012 to 2019. DNA content in cells from pleural effusions was detected by computer aided DNA ploidy quantitative analysis. Percentages of cells with greater than 5c，the number of cells with greater than 9c，the maximum DNA index (DI) value，the average DI value of cells with greater than 5c and the peak of aneuploid cells were calculated. Differences of DNA ploidy and EGFR gene mutation among groups were compared，and correlations between DNA ploidy and EGFR mutation were tested to analyze the values of DNA ploidy and EGFR gene mutation in prognosis of lung adenocarcinoma. RESULTS：EGFR mutations were detected in 244 (55.58%) of 439 patients. The mutation rate was significantly reduced in male patients，and in patients with a history of smoking，compared to the controls (P<0.05). In addition，the percentage of cells greater than 5c <14%，the number of cells greater than 9c <8，the maximum DI value <6，and the mean value of cells greater than 5c <5 (P<0.05). The mutation rate of EGFR gene was different with different aneuploid cell peak，and compared with the nonpeak group，the mutation rate of EGFR gene was higher with single and double peak (P<0.05)，while there was no significant difference in EGFR mutation rate between multi-peak and other groups. Compared with the EGFR wild-type patients，EGFR mutant patients had a higher mean rank in the percentage of cells greater than 5c，the number of cells greater than 9c，the maximum DI，the mean DI of cells greater than 5c，and the aneuploid cell peak number，and all five indexes were weakly positively correlated with EGFR mutation. Univariate survival analysis showed that the median overall survival time of patients with greater than 5c cell percentage ≥14%，greater than 9C cell number ≥8 and EGFR mutation were longer than that of the controls. Multivariate survival analysis showed that DNA ploidy was not associated with patient prognosis，and EGFR gene mutation was an independent prognostic factor in patients with advanced lung adenocarcinoma. CONCLUSION：There was a positive correlation between EGFR gene mutation and DNA ploidy abnormality in patients with advanced lung adenocarcinoma，and DNA ploidy abnormality was a potential predictor of EGFR gene mutation. DNA ploidy was not an independent prognostic factor in patients with advanced lung adenocarcinoma. Patients with EGFR gene mutation had a better prognosis than the wild-type patients.

Key words: DNA ploidy abnormality, EGFR mutation, lung adenocarcinoma, computer aided, prognosis