Monocyte-to-lymphocyte ratio as a subtype-specific biomarker in breast cancer prognosis: a narrative review

Breast cancer is a biologically diverse condition featuring unique molecular subtypes that affect prognosis and treatment response. The monocyte-to-lymphocyte ratio (MLR), obtained from peripheral blood counts, has surfaced as a potential inflammatory biomarker indicating the equilibrium between tumor-supporting monocytes and antitumor lymphocytes. This review discusses the function of MLR as a subtype-specific biomarker in breast cancer, emphasizing its potential value in forecasting disease advancement, treatment efficacy, and overall patient results. Evidence shows that increased MLR is linked to poor outcomes in various breast cancer subtypes, such as hormone receptor-positive, human epidermal growth factor receptor 2-enriched, and triple-negative breast cancers. The biological basis arises from the dual function of monocytes in promoting tumor-supportive environments and lymphocytes in facilitating immune monitoring. Through the capture of this immunological interaction, MLR acts as a low-risk and affordable method for risk assessment and treatment choices adapted to molecular subtype traits.