Vol. 9, Issue 4, Part A (2025)

Background: Breast cancer remains the most prevalent malignancy among women worldwide and represents a major cause of cancer-related mortality. Metastasis is the leading determinant of poor prognosis and mortality in breast cancer patients. Molecular subtyping, including Luminal A, Luminal B, HER2-positive, and Triple Negative Breast Cancer (TNBC), has been recognized as an important prognostic and predictive factor influencing the metastatic potential. In addition, histological differentiation grade reflects tumor aggressiveness and correlates with disease progression. However, the association between molecular subtype, histological differentiation, and metastasis remains controversial across studies and populations. Objective: To investigate the relationship between molecular subtypes and differentiation degree of breast cancer with the occurrence of metastasis among patients at Dr. M. Djamil General Hospital, Padang, Indonesia. Methods: A cross-sectional study was conducted on female breast cancer patients diagnosed between January 2020 and December 2024 who underwent immunohistochemistry evaluation for ER, PR, HER2, and Ki-67. Molecular subtypes were classified into Luminal A, Luminal B, HER2-type, and TNBC, while histological grading was assessed based on the Nottingham Grading System. Data were obtained from medical records and analyzed using Chi-square test, with a significance level set at p<0.05. Results: A total of 90 patients were included, with 82.2% aged ≥40 years. Luminal B subtype was the most prevalent (43.3%), followed by HER2-type (25.6%), TNBC (18.9%), and Luminal A (12.2%). Most patients had grade II tumors (56.7%), and 82.2% had metastasis. There was a significant association between molecular subtypes and metastasis (p = 0.017), with Luminal B and HER2-type showing the highest metastatic proportion. No significant relationship was found between differentiation grade and metastasis (p = 0.367). Conclusion: Molecular subtypes, particularly Luminal B and HER2-type, were significantly associated with breast cancer metastasis, whereas differentiation degree did not show a significant correlation. These findings underscore the importance of molecular profiling in predicting disease spread and guiding individualized therapy for breast cancer patients.