# Pathological features of BRCA-mutated breast cancer in Shenzhen, China: a single-center study

## TL;DR

This study compares the characteristics of breast cancer in BRCA-mutated and non-mutated patients in Shenzhen, China, finding differences in tumor size, grade, and subtype.

## Contribution

The study provides new insights into BRCA-mutated breast cancer features in a Chinese population, specifically in Shenzhen.

## Key findings

- BRCA-mutated patients had smaller tumors (≤2 cm) compared to non-mutated patients.
- BRCA-mutated tumors were more likely to be grade III and triple-negative breast cancer (TNBC).
- ER, PR, and Ki-67 expression levels differed significantly between the two groups.

## Abstract

Most studies on breast cancer susceptibility gene (BRCA) mutations have focused on Caucasian populations in Europe and North America. Currently, there is a lack of literature and data research in related fields in Shenzhen, China, and even in Guangdong Province. This study aims to establish a registry of BRCA mutation carriers by analyzing and comparing the pathological features of breast cancer patients carrying and not carrying BRCA mutations in the Shenzhen area.

Blood samples were collected from 406 breast cancer patients who met the inclusion criteria (from July 2016 to November 2024) and genetic testing was performed using next-generation sequencing (NGS) technology. Patients were divided into two groups: BRCA mutation group with 54 cases and BRCA non-mutation group with 352 cases. A retrospective analysis was conducted on patient data collected from the health information system of Shenzhen People’s Hospital, including demographic data, clinical pathological characteristics, and variables related to molecular typing. We used SPSS software for statistical analysis of the data.

In 406 breast cancer patients, the average age of the BRCA mutation group was 39.3 ± 9.2 years, while the average age of the BRCA non-mutation group was 41.8 ± 8.8 years. The proportion of tumors ≤ 2 cm in the mutation group is 72.2%, higher than the 53.1% in the non-mutation group (P = 0.009, 95% confidence interval [1.220–4.313]). The proportion of grade III pathologic grading in the mutation group is 59.3%, higher than the 36.1% in the non-mutation group (P = 0.001, 95% confidence interval [1.436–4.625]). In the mutation group, there are seven cases of Luminal A (13.0%), zero cases of Luminal B (Her-2 positive) (0%), and 23 cases of triple-negative breast cancer (TNBC) (42.6%). In the non-mutation group, there are 93 cases of Luminal A (26.4%), 54 cases of Luminal B (Her-2 positive) (15.3%), and 67 cases of TNBC (19.0%). (Luminal A: P = 0.033, 95% confidence interval [0.181–0.950]; Luminal B (Her-2 positive): P = 0.002; TNBC: P < 0.001, 95% confidence interval [1.730–5.759]). The expression levels of estrogen receptor (ER) (P = 0.009), progesterone receptor (PR) (P < 0.001), and Ki-67 (P < 0.001) show significant differences between the BRCA mutation group and the BRCA non-mutation group.

Compared to BRCA non-mutated patients, BRCA mutated patients in Shenzhen have smaller tumor volumes, with pathological grades mainly at grade 3, and molecular subtypes predominantly being triple-negative breast cancer.