ASSOCIATION BETWEEN MOLECULAR SUBTYPES AND SITES OF METASTASIS IN BREAST CANCER

Background: Breast cancer is a leading cause of cancer-related mortality worldwide, with metastasis contributing significantly to poor outcomes. Molecular subtypes are known to exhibit different metastatic patterns; however, findings remain inconsistent. This study aimed to evaluate the association between molecular subtypes and metastatic sites in breast cancer. Methods: A cross-sectional analytical study was conducted at Saiful Anwar General Hospital, Malang, Indonesia, from July to December 2025. Metastatic site data were obtained from medical records, and molecular subtypes were determined by immunohistochemistry. Data were analyzed using the chi-square test, with p < 0.05 considered statistically significant. Results: A total of 94 patients were included. The lung was the most common metastatic site (58.5%), followed by bone (33.0%) and liver (4.3%). Luminal A was the predominant subtype (57.45%). Liver metastasis was significantly associated with molecular subtype (p < 0.001), whereas no significant associations were found for lung, bone, or other metastatic sites. Conclusion: Liver metastasis is significantly associated with breast cancer molecular subtypes.