Collateralization of the upper extremity lymphatic system after axillary lymph node dissection

Background: Lymphatic drainage from the arm may be altered after axillary lymph node dissection (ALND). Understanding these alterations is important as they may change standard surgical and radiation treatment in recurrent breast cancer or upper extremity skin cancers, including melanoma. Methods: Utilizing a single-institution planar and single photon emission computed tomography/computed tomography lymphoscintigraphy database, we identified patients with a diagnosis of upper extremity cutaneous melanoma from 2008 to2023 who previously underwent ALND for cancer treatment and did not develop upper extremity cancer-related lymphedema. ALND patients were matched to control patients presenting with cutaneous melanomas at the same anatomic sites. Sentinel lymph nodes (SLNs) were compared between both groups. Results: Of 3628 upper extremity melanoma cutaneous patients, 934 met inclusion criteria, including 22 ALND and 912 control patients. Level I axillary SLN drainage was observed in 98% of controls and 27% of ALND patients (p< 0.001). Level IIaxillary SLN drainage was observed in 3% of controls and 27% of ALND patients(p< 0.001). Level III axillary SLN drainage was observed in 1% of controls and 32% of ALND patients (p< 0.001). Epitrochlear SLN drainage was observed in 9% of controls and 32% of ALND patients, respectively (p< 0.046). Brachial SLN drainage was observed in 4% of controls and 23% of ALND patients (p< 0.001). Conclusions: Distinct changes in functional lymphatic drainage were seen between the arms of patients who previously underwent ALND versus control patients. Levels II and III axillary, epitrochlear, and brachial nodes are possible sites of metastatic disease that should be considered in patients with a prior ALND.