A level III sentinel lymph node in breast cancer

BACKGROUND: For accurate nodal staging, all blue and radioactive lymph nodes should be sampled during the sentinel lymph node biopsy for breast cancer. We report a case of anomalous drainage in which one of the sentinel lymph nodes was unexpectedly found in the level III axillary space. CASE PRESENTATION: A 40-year-old female underwent mastectomy for extensive high-grade ductal carcinoma in-situ (DCIS) with micro-invasion. The index lesion was located in the right upper inner quadrant. Lymphoscintigraphy was performed on the morning of surgery. Two sentinel lymph nodes were identified. At operation, 5 mls of isosulfan blue dye was injected at the same site of the radio-colloid injection. The first sentinel lymph node was found at level I and was blue and radioactive. The second sentinel node was detected in an unexpected anomalous location at level III, medial to the pectoralis minor. Both sentinel nodes were negative. CONCLUSION: Sentinel node staging can lead to unexpected patterns of lymphatic drainage. For accurate staging, it is important to survey all potential sites of nodal metastasis either with preoperative lymphoscintigraphy and/or rigorous examination of regional nodal basins with the intra-operative gamma probe.