SPECT/CT scans allow precise anatomical location of sentinel lymph nodes in breast cancer and redefine lymphatic drainage from the breast to the axilla

Abstract Background Historical studies of lymphatic drainage of the breast have suggested that the lymphatic drainage of the breast was to lymph nodes lying in the antero-pectoral group of nodes in the axilla just lateral to the pectoral muscles. The purpose of this study was to confirm this is not correct. Methods The hybrid imaging method of SPECT/CT allows the exact anatomical position of the sentinel lymph node (SLN) in the axilla to be documented during pre-operative lymphoscintigraphy (LS) in patients with breast cancer. We have done this in a series of 741 patients. The Level I axillary nodes were defined as anterior, mid or posterior. This was related to the anatomical location of the primary cancer in the breast. Results A SLN was found in the axilla in 97.8% of our patients. Just under 50% of SLNs located in the axilla were not in the anterior group and lay in the mid or posterior group of Level I axillary nodes. There was a SLN in a single node field in 460 patients (63%), two node fields in 261(36%), three node fields in 6 and four node fields in 1 patient. Conclusion Axillary lymphatic drainage from the breast is not exclusively to the anterior (or antero-pectoral) group of Level I nodes. Synopsis SPECT/CT lymphoscintigraphy shows that the breast does not always drain to the anterior group of Level I lymph nodes in the axilla but may drain to the mid axilla and/or posterior group in about 50% of patients with breast cancer regardless of the location of the cancer in the breast. These data redefine lymph drainage from the breast to axillary lymph nodes.