Breast cancer (BC) is the most common malignancy in women. We retrieved medical records from >2,000 Chilean BC patients over the 1997–2018 period. The objective was to assess changes in clinical presentation or prognosis of our patients throughout these 20 years of practice. Although most variables did not display significant variations, we observed a progressive increase in stage IV BC over this period. Our data showed that tumour stage III/IV or HER2-enriched subtype tumours were associated with poorer prognosis. In contrast, we found that patients diagnosed by mammography had better overall survival. We speculate that better screenings and more sensitive imaging could explain the unexpected rise in stage IV cases. Our results support mammography screenings as an effective measure to reduce BC-related mortality.