Is risk of axillary lymph node metastasis associated with proximity of breast cancer to the skin?
INTRODUCTION: Risk of axillary lymph node metastasis, the most important predictor of disease-free and overall survival in breast cancer patients, is estimated primarily from histologic features of the primary cancer including tumor size, histologic type and grade, and hormone receptor expression. Based upon a clinical impression, and research showing that palpable cancers are more likely to be node positive, we hypothesized that primary breast cancers more proximal to the skin of the breast are more likely to be positive for axillary lymph node metastasis. METHODS: This is a retrospective medical record review of 209 women with stage T1 or T2 (</=5.0 cm) invasive breast cancer who received dedicated breast ultrasound at a single mammography clinic in Columbia, South Carolina, between 1997 and 2002. RESULTS: None of the 26 cancers more than 14 mm from the skin had metastasized to axillary lymph nodes. In logistic regression modeling only tumor size, histologic grade and tumor proximity to the skin (as a categorical variable) were significantly associated with odds of axillary metastasis. Among cancers within 14 mm of the skin, proximity was not an independent predictor. CONCLUSIONS: Stage T1 and T2 breast cancers located less proximally to the skin may be less likely to spread to the axillary lymph nodes. We observed what appears to be a threshold at approximately 14 mm from the skin (based upon this group of patients): none of 26 cancers below this level had spread to axillary nodes. Further research is needed to confirm these provocative findings.