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.