Lower and central tumor location correlates with lymphoscintigraphy drainage to the internal mammary lymph nodes in breast carcinoma

BACKGROUND. Radiation to the internal mammary chain (IMC) may be indicated for breast carcinoma patients with positive axillary sentinel lymph nodes (SLNs) and lymphoscintigraphic evidence of drainage to the IMC. The purpose of this study was to identify predictors of IMC drainage in patients with positive axillary SLNs. METHODS. The records of 297 breast carcinoma patients with positive axillary SLNs and preoperative lymphoscintigraphy were reviewed between 1995 and 2002. Radiolabeled colloid was injected peritumorally with lymphoscintigraphy performed 30-60 minutes later. Drainage to the regional nodes of 279 patients was seen on lymphoscintigraphy. Associations among patient and tumor-related factors and drainage to the IMC were examined. RESULTS. Drainage to the IMC on lymphoscintigraphy was seen in 63 patients (21%). IMC drainage only occurred in 4 patients, and 59 patients had both axillary and IMC drainage. The only variable that correlated with IMC drainage was tumor location (P = 0.017). Rates of drainage to the IMC were 14.1% for upper outer quadrant (n = 128), 16.7% for upper inner quadrant (n = 30), 31.6% for lower outer quadrant (n = 19), 42.9% for lower inner quadrant (n = 14), and 28.4% for central tumors (n = 88). IMC drainage rates differed significantly between upper and lower tumors (lower 36.4% vs. central 28.4% vs. upper 14.6%, P = 0.003) but not between medial and lateral tumors (medial 25.0% vs. central 28.4% vs. lateral 16.3%, P = 0.077). CONCLUSIONS. Patients with tumors in the lower or central breast and positive axillary SLNs have increased incidence of drainage to the IMC. Preoperative lymphoscintigraphy can help to define the nodal basins at risk for harboring disease.