Purpose To investigate the clinicopathological characteristics and genetic variations of stage Ⅰ lung adenocarci-noma with high-grade components,according to the new grading system of the WHO classification of thoracic tumors(2021).Methods A retrospective analysis was conducted on the clini-cal data of 785 patients with stage Ⅰ lung adenocarcinoma.HE,EnVision immunohistochemistry and Victoria blue staining were used,common genetic variation(EGFR/KRAS/ALK/ROS1/RET)were detected by PCR method.The correlation between different high-grade components and clinical pathological charac-teristics as well as genetic variations in stage Ⅰ lung adenocarci-noma were analyzed.Results A total of 785 cases of stage Ⅰlung adenocarcinoma were enrolled,including 332 cases with high-grade components and 453 cases without high-grade compo-nents.Among the adenocarcinomas with high-grade components,there were 7 cases of grade 1,150 cases of grade 2,and 175 ca-ses of grade 3.The positive rates of tumor cells spreading through airspace(STAS),vascular invasion,and pleural inva-sion in grade 2 adenocarcinoma with two high-grade components(61.5％,21.2％,26.9％)were significantly higher than that of the adenocarcinomas with only one high-grade component(20.4％,7.1％,5.1％),but there was no significant differ-ence in grade 3 adenocarcinoma.The positive rate(39.0％)of STAS in the micropapillary group with one high-grade component in grade 2 adenocarcinoma was significantly higher than that in the complex glandular group(9.3％)and the solid group(0),while there was no significant difference between the latter two groups.Among the three groups there were no statistically signif-icant differences in grade 3 adenocarcinoma.In 167 cases of ad-enocarcinoma with two or more high-grade components,there were 74 cases(44.3％)of complex glands combined with mi-cropapillary components,67 cases(40.1％)of complex glands combined with solid components,8 cases(4.8％)of micropap-illary combined with solid components,and 18 cases(10.8％)of three types of components.The positive rates of pleural inva-sion and KRAS gene mutation or fusion gene(ALK/ROS1/RET)in the group of complex glands combined with solid(49.3％,28.3％)were significantly higher as compared to those in the group of complex glands combined with micropapil-lary(27.0％,8.6％).The positive rate of psammoma bodies in the group with high-grade components(24.7％)was significant-ly higher than that in those without high-grade components(3.5％,P＜0.001),and the positive rate of psammoma bodies in group of gene mutation(EGFR/KRAS)(40.4％)was higher than that in the no-gene mutation group(26.7％,P＜0.05).Conclusion The clinicopathological features of different high-grade components in stage Ⅰ lung adenocarcinoma are not identi-cal,suggesting that their invasiveness may have different biologi-cal backgrounds.Characteristic morphological observations are helpful.