Also, subtype-specific analysis revealed that prognostically relevant eccDNA features were identified in luminal-A (satellite and simple-repeat-annotated eccDNA proportion, p < 0.05) and luminal-B (DHS-annotated eccDNA proportion, p < 0.05) breast cancers (Figure S12), while no significant associations were observed in the HER2-enriched and TNBC subtypes, likely due to limited sample sizes. This evidence concerns the gene ERBB2 and breast cancer.