Relationship between the changes of positivity rate of HER2 expression and the diameter of invasive lesions in early breast cancer and its clinical significance

Abstract

Background: The expression status of HER2 is an important factor in evaluating the prognosis of breast cancer. We found that the positivity rate of HER2 varied with the diameter of invasive lesions in early breast cancer.We aimed to explore the relationship between the change of HER2 positivity rate of early breast cancer and the diameter of the invasive foci and its clinical significance.

Methods: A total of 217 patients with microinvasive breast cancer and T1a stage breast cancer were enrolled in this study. Machine learning algorithm was used to extract morphological features of invasive lesions in early breast cancer. Using Spearman to analysis the clinicopathological and morphological features related to HER2 expression McNemar test was used to analyze the consistency of HER2 expression between the carcinoma in situ area and the invasive cancer area.

Results: In early breast cancer, the diameter of the invasive foci was strongly negatively correlated with the expression status of HER2 (rho=-0.468, p < 0.001). As the diameter of the invasive foci increases, the HER2 positivity rate gradually decreases. When the diameter of the invasive foci> 2 mm, the positivity rate of HER2 was significantly reduced (from 52.6% to 16.1%, p < 0.001), which was close to the positivity rate of HER2 in ordinary invasive breast cancer. Moreover, most of the clinicopathological characteristics of breast cancer with an invasive lesion diameter of 1-2 mm and DCIS-MI were not significantly different (p > 0.05). Among 217 patients, the consistency rate of HER2 expression in carcinoma in situ and invasive foci areas was 97.7% (212/217), and there was no significant difference in HER2 expression status (p = 0.25 and p = 0.50, respectively).

Conclusions: We recommend that breast cancer with an invasive lesion diameter of 1-2 mm should be classified as microinvasive breast cancer. In early breast cancer,the expression status of HER2 in the invasive foci area can refer to the HER2 expression status in carcinoma in situ area. However, it needs further support from a large amount of data and follow-up results.

Keywords: Consistency analysis; Diameter of the invasive foci; Early breast cancer; HER2; Microinvasive breast cancer.