Abstract

Background: Germline pathogenic variants (PVs) in the ataxia-telangiectasia mutated (ATM) gene are established moderate-risk factors for breast cancer (BC), however, population-specific variant spectra and the clinical significance of many missense variants remain incompletely characterized.

Aims: To evaluate the prevalence of ATM variants in a large cohort of patients with BC from North Macedonia and compare it with that in the general population, with a particular focus on the frequency of the p.(Leu2492Arg) variant and its distribution relative to global genomic datasets.

Study Design: This study was conducted as a retrospective case–control analysis.

Methods: ATM variants were analyzed in 1,211 patients with BC from North Macedonia using a targeted hereditary cancer gene panel. These findings were compared with those from 1,303 population-based controls analyzed by clinical exome or whole-exome sequencing.

Results: Pathogenic ATM variants were identified in 1.9% of BC cases and 0.4% of controls, indicating a significantly increased risk of BC [odds ratio (OR) = 5.02, p = 0.0006]. Most PVs were protein-truncating, with six recurrent variants accounting for over 70% of detections, suggesting regional enrichment. Carriers showed a significantly higher prevalence of human epidermal growth factor receptor 2-positive tumors (OR = 2.92, p = 0.0189). Variants of uncertain significance were observed at comparable frequencies in cases and controls. The p.(Leu2492Arg) missense variant was more frequently detected in cases than in controls (1.9% vs. 1.1%; OR = 1.78, p = 0.086) and exhibited a markedly higher allele frequency in this population than in global databases.

Conclusion: These findings confirm ATM as a clinically relevant BC susceptibility gene in North Macedonia and highlight the population-specific enrichment of both PVs and the p.(Leu2492Arg) missense variant. The results emphasize the importance of using population-matched controls and regional genomic data for accurate risk assessment and variant interpretation.