HER2 in gynecological malignancies: Bridging the gap between standardized pathological assessment and precision therapy

Abstract

HER2 is a transmembrane tyrosine kinase receptor involved in cell proliferation, survival, and differentiation. While its role in breast and gastric cancers is well established, increasing attention is being paid to HER2 expression in gynecologic malignancies. In endometrial cancer, HER2 overexpression is most commonly associated with serous endometrial carcinoma (SEC), where it occurs in approximately 30 % of cases and correlates with poor prognosis, platinum resistance, and TP53 mutations. HER2-low expression, defined by IHC scores of 1 + or 2 + without gene amplification, has also emerged as a potential therapeutic target. Trastuzumab-based therapy has shown survival benefit in HER2-positive SEC, leading to its inclusion in current treatment guidelines. In ovarian cancer, HER2 amplification is most frequent in mucinous subtypes but also appears in clear cell and endometrioid carcinomas. The prognostic value remains debated, though recent trials of antibody–drug conjugates (e.g., T-DXd) show promise. In cervical cancer, HER2 is more commonly expressed in adenocarcinomas, particularly gastric-type variants, with gene amplification linked to adverse features. HER2 positivity is rare in vulvar and vaginal cancers but is notably present in extramammary Paget disease. Accurate HER2 testing relies on IHC with ISH confirmation and may be complemented by NGS or PCR in select cases. Diagnostic challenges include variable scoring systems, intratumoral heterogeneity, and HER2-low classification. Standardization of testing criteria and further clinical validation of HER2-targeted strategies across gynecologic tumors are essential to guide personalized therapy and improve outcomes.