Background: Variables such as tumor size, histology, and grade, tumor biology, presence of lymphovascular invasion, and patient age have been shown to impact likelihood of nodal positivity. The aim of this study is to determine whether primary location of invasive disease within the breast is associated with nodal positivity. Patients and Methods: Patients with invasive breast cancer undergoing axillary staging from 2010 to 2014 were identified from the National Cancer Data Base. Rates of axillary nodal positivity by primary tumor locations were compared, and multivariable analysis performed using logistic regression to control for factors known to impact nodal positivity. Results: A total of 599,722 patients met inclusion criteria. Likelihood of nodal positivity was greatest with primary tumors located in the nipple (43.8%), followed by multicentric disease (40.8%), central breast lesions (39.4%), and axillary tail lesions (38.4%). Tumor location remained independently associated with nodal positivity on multivariable analysis adjusting for variables known to affect nodal positivity with odds ratio 2.8 for tumors in the nipple [95% confidence interval (CI) 2.5–3.1], 2.2 for central breast (95% CI: 2.2–2.3), and 2.7 for axillary tail (95% CI: 2.4–2.9). When restricted to patients with clinically negative nodes (n = 430,949), a similar association was seen. Conclusion: Patients with invasive breast cancer located in the nipple, central breast, and axillary tail have the highest risk of positive axillary lymph nodes independent of patient age, tumor grade, biologic subtype, histology, and size. This should be considered along with other factors in preoperative counseling and decision-making regarding plans for axillary lymph node staging.
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