Objective To investigate the clinicopathological features,molecular typing and prognosis of human epidermal growth factor receptor 2(HER2)low expression breast cancer.Methods We retrospectively collected 1,684 cases of primary invasive breast cancer patients diagnosed and treated in the Breast Disease Center of Zhejiang Provincial Hospital of Chinese Medicine from January 2016 to September 2021,including 1,023 cases of invasive ductal carcinoma,and 805 breast cancer patients with HER2-negative.The differences of clinicopathological features,molecular typing and survival prognosis between HER2-low and HER2-zero breast cancer patients were compared.Kaplan-Meier method was used to plot the survival curves of DFS and BCSS in the two groups.Log-rank test was used to compare the survival differences.Univariate and multivariate Cox proportional hazard regression models were used to analyze the prognostic factors.Results Of the 805 patients with HER2-negative breast cancer,515(64.0%)had HER2 zero expression and 290(36.0%)had HER2 low expression.HER2-low breast cancer accounted for 28.3%of all breast invasive ductal carcinoma,and the molecular typing was mainly Luminal B type.Compared with the HER2-zero group,the proportion of N stage Ⅱ～Ⅲ(P=0.004),TNM stage 3(P=0.002)and HR positive patients(P=0.002)in the HER2-low group was higher.Among the 805 patients,629(78.1%)were HR positive and 176(21.9%)were HR negative.Of the 629 HR-positive patients,385(61.2%)had HER2 zero expression and 244(28.8%)had HER2 low expression.Compared with the HER2-zero group,the HER2-low group had a younger age at diagnosis(P=0.031),a higher proportion of patients<45 years old(P=0.003),N stage Ⅱ～Ⅲ(P=0.001),and TNM stage 3(P=0.001).Among the 176 HR-negative patients,130(73.9%)had HER2 zero expression and 46(26.1%)had HER2 low expression.Compared with the HER2-zero group,the patients in the HER2-low group were older at diagnosis(P=0.047),had a higher proportion of patients≥45 years old(P=0.036),and had lower histological grade(P<0.001)and Ki-67 proliferation index(P=0.027).Conclusion HER2-low breast cancer accounts for 28.3%of all breast invasive ductal carcinoma,with unique clinicopathological features and molecular typing.HR status may be the main driver of the biological behavior of HER2-low breast cancer.There is no significant difference in survival prognosis between HER2-low and HER2-zero breast cancer patients.
Human epidermal growth factor receptor 2Low expressionBreast cancerClinicopathological featuresMolecular typingPrognosis
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