What question did this study set out to answer?

To determine the distribution of hereditary breast cancer molecular subtypes based on the presence of pathogenic or likely pathogenic genetic variants.

February 22, 2026

Abstract PS3-03-16: Distribution of Molecular Subtypes of Hereditary Breast Cancer in Brazilian Patients according to Pathogenic or Likely Pathogenic Germline Genetic Variants

Key Points

To determine the distribution of hereditary breast cancer molecular subtypes based on the presence of pathogenic or likely pathogenic genetic variants.
Conducted a prospective cohort study from November 2021 to October 2022
Included women under follow-up at a high-risk outpatient clinic
Patients underwent genetic testing based on specific familial and personal cancer histories
Pathogenic or likely pathogenic variants were found in 36% of patients
Molecular subtypes most associated with these variants included Luminal B HER2-negative and triple-negative
Notable odds ratios were identified for these subtypes when analyzing BRCA1, BRCA2, and non-BRCA genes

Abstract

Abstract Objective: To assess the distribution of molecular subtypes of hereditary breast cancers, according to the presence of pathogenic or likely pathogenic germline genetic variants detected by multigene panel testing. Methods: A prospective cohort study was conducted from November 2021 to October 2022, involving women under follow-up at the high-risk outpatient clinic at the University of Campinas (UNICAMP). Patients were required to meet the following criteria: a personal history of luminal or HER2-positive breast cancer diagnosed before age 45, or triple-negative breast cancer diagnosed before age 60, along with at least one first- or second-degree relative with breast, ovarian, and/or prostate cancer, or who met the NCCN high-risk criteria (NCCN version 3.2021). Patients completed a questionnaire, after which they were referred for genetic testing. Following the test results, they received counseling based on the findings. Results: A total of 184 patients and 198 breasts were studied. Pathogenic variants (PV) or likely pathogenic variants (LPV) were detected in 36% (67/184) of the patients. Approximately 28% (51/184) were under 40 years of age, 30% (74/184) were non- Caucasian, and 49% (90/184) were premenopausal. General Analysis: The molecular subtypes most associated with pathogenic/probably pathogenic variants (PV/LPV) were Luminal B HER2-negative "like" (OR=11.76; CI 4.19-33.01) and triple-negative (OR=8.4; CI 3.45-20.43). These associations remained consistent even when the analysis was restricted to BRCA1 and BRCA2 genes only (OR=9.33; CI 2.00-29.99) (OR=9.03; CI 3.37-24.20) or to non-BRCA genes (OR=7.75;CI 2.96-29.44) (OR=3.48; CI 1.32-9.20) for Luminal B HER2-negative "like" triple-negative subtypes. Conclusion: Two molecular subtypes were associated with the presence of pathogenic or likely pathogenic variants in genes associated with hereditary breast cancer: Luminal B HER2-negative and triple-negative subtypes. Keywords: High risk; Germline variants; Genetic testing; Breast cancer; Molecular subtypes Citation Format: A. R. cabello, C. Cabello, S. Ramalho, C. E. Alem, S. R. Teixeira, L. R. Silva, G. S. Paiva, B. N. Duarte, M. Souza, T. cabello, D. I. Silva, A. Viaro, T. Gaspar, L. C. Zeferino. Distribution of Molecular Subtypes of Hereditary Breast Cancer in Brazilian Patients according to Pathogenic or Likely Pathogenic Germline Genetic Variants abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-03-16.

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