Use of Lymphoscintigraphy Defines Lymphatic Drainage Patterns Before Sentinel Lymph Node Biopsy for Breast Cancer

Background: Lymphoscintigraphy (LSG) can identify lymphatic drainage patterns before sentinel lymph node (SLN) biopsy is performed in patients with early-stage breast cancer, but the importance of extraaxillary SLNs seen on LSG is unknown. We assessed whether drainage patterns seen on LSG were associated with histologic findings in axillary SLNs recovered at SLN biopsy. Study design: From a prospectively maintained database, we identified 1,201 clinically node-negative patients with invasive breast cancer who underwent preoperative LSG and axillary SLN biopsy. Patient and tumor characteristics, LSG results, and final SLN pathology results were examined. Results: LSG showed drainage to internal mammary (IM) nodes in 1.6% of patients, axillary nodes in 68.1%, both IM and axillary nodes in 19.8%, and no drainage in 10.3%. Drainage to IM nodes was observed for tumors in all quadrants of the breast. Patients with IM drainage had a younger median age than patients without IM drainage (51.8 versus 58.3 years, respectively; p < 0.001). The intraoperative axillary SLN identification rate was higher when axillary drainage was observed on LSG than when it was not observed (98.7% versus 93.0%, respectively; p < 0.001), but the LSG drainage pattern was not associated with pathologic status of the SLN or number of metastatic SLNs. At a median followup of 32 months, 4 patients had regional nodal recurrence. Conclusions: Almost one-fourth of patients had lymphatic drainage to the extraaxillary lymph nodes, particularly the IM nodes, seen on LSG. Extraaxillary drainage seen on LSG did not preclude identification of axillary SLNs at operation. Longterm followup of patients with lymphoscintigraphic evidence of extraaxillary drainage is needed to determine whether regional and systemic recurrence patterns differ in these patients.