Comparison of the distribution of lymph node metastases compared to healthy lymph nodes in breast cancer.

Background Current literature lacks a comparison of lymph node metastases and non-pathological lymph nodes distribution in breast cancer patients. The aim of the current retrospective study was to generate a comprehensive atlas of the lymph node system. Methods 143 breast cancer patients underwent F-18-FDG-PET/CT (PET/CT) imaging for staging purposes and were diagnosed with regional lymph node metastases. Based on the PET/CT data set a total of 326 lymph node metastases and 1826 non-pathological lymph nodes were detected and contoured manually in the patient collective. Using rigid and deformable registration algorithms all structures were transferred to a template planning CT of a standard patient. Subsequently, a 3D-atlas of the distribution of lymph node metastases and non-pathological lymph nodes were generated and compared to each other. Results Both, lymph node metastases and non-pathological lymph nodes, accumulated in certain areas ("hot-spots") within the lymphatic drainage system. However large differences regarding the distribution patterns were detected: lymph node metastases hot spots occurred in close proximity to the subclavian vein in level I-III, whereas the non-pathological lymph nodes accumulated mostly (within a wider range) in level I. In level II and III lymph node metastases exceeded clearly the areas in which non-pathological lymph nodes occurred. Conclusion Lymph node metastases and non-pathological lymph node distribution within the lymph node system differ clearly. Based on our results, an individual adjustment of the CTV in order to include visible lymph nodes in level II and III should be discussed