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proLékaře.cz / Journals / Czecho-Slovak Pathology / 2025 - 4

Immunohistochemical assessment of HER2 protein in breast carcinomas –⁠ current status

Czech version

Authors: Pavel Fabian
Authors‘ workplace: Oddělení onkologické patologie, Masarykův onkologický ústav, Brno
Published in: Čes.-slov. Patol., 61, 2025, No. 4, p. 190-194
Category: Reviews Article

Overview

The existing HER2 immunohistochemistry testing is currently experiencing changes in its scoring caused by the recent clinical trials results, especially DESTINY Breast 04 and 06. These trials demonstrated that any detectable immunohistochemical positivity of HER2 protein on tumor cells is a predictor of response to the new antibody-drug conjugate trastuzumab deruxtecan. These studies introduced new terms “HER2 low” and later “HER2 ultralow” to distinguish subgroups within the original category “HER2 negative”, which quickly became accepted in clinical practice. This article aims to explain these new terms and present Czech and international expert recommendations for testing and reporting of HER2 immunohistochemistry in relation to these new categories.

Keywords:

trastuzumab deruxtecan – HER2 immunohistochemistry – HER2 low

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