HER2 testing in multifocal/multicentric breast cancer: should all foci be tested in the context of HER2-low and HER2-ultralow?

ABSTRACT:

Background

Current guidelines for HER2 testing in multifocal and multicentric breast cancer (MMBC) are typically based only on the evaluation of the main focus, which may lead to underdetection of HER2-low and HER2-ultralow, potentially resulting in missed treatment opportunities with trastuzumab deruxtecan. Therefore, this study aimed to evaluate the heterogeneity of HER2 expression among different foci in MMBC and to assess the clinical applicability of current HER2 testing strategies.

Methods

A retrospective collection of all invasive cancer foci specimens was conducted from 490 consecutive MMBC patients, with HER2 testing and evaluation performed on each individual focus.

Results

In the binary classification of HER2-negative and HER2-positive cases, 4.0 % of cases

SUBMITTER: Wu S 

PROVIDER: S-EPMC12475518 | biostudies-literature | 2025 Sep

REPOSITORIES: biostudies-literature