When Biology Bests Clinical Assumptions About Breast Cancer

When determining breast cancer prognoses and appropriate therapeutic approaches, clinicians often estimate recurrence risk based on tumor size and nodal status. Such estimates usually are guided by fundamental principles — e.g., larger tumors are more likely to have nodal involvement and poorer prognoses. However, unexpected situations can arise in which extremely small tumors have spread to multiple axillary lymph nodes or, conversely, large tumors have no axillary nodal involvement. Also, the clinical impression is mounting that triple-negative disease (negative for estrogen receptors [ERs], progesterone receptors, and human epidermal growth factor receptor 2 [HER2]) is “simply bad” regardless of tumor size or nodal status. Although these…