Epitrochlear sentinel lymph nodes in melanoma: interval or independent?

Most primary melanomas on the distal upper extremity metastasize to a sentinel lymph node (SLN) in the axillary basin, but occasionally a primary melanoma will drain to the epitrochlear basin. The relationship between tumor-draining axillary and epitrochlear SLNs is unclear. We hypothesize that the epitrochlear SLN functions in an interval manner with the axillary lymph node basin. We queried our melanoma database to identify patients who underwent SLN biopsy for a distal upper-extremity melanoma. Patient demographics, tumor characteristics, patterns of nodal drainage, and incidence of SLN metastasis were analyzed. Of 255 patients identified, 38 (14.9%) had an epitrochlear SLN. Mean Breslow thickness was 2.26 mm. All patients with epitrochlear drainage had concurrent axillary drainage and underwent axillary and epitrochlear SLN biopsies. Of these 38 patients, two (5.2%) had epitrochlear and axillary SLN metastasis, four (10.5%) had epitrochlear metastasis only, four (10.5%) had axillary metastasis only, and the remaining 28 (73.7%) had tumor-free SLNs. The invariable association of epitrochlear and axillary drainage in this study suggests that epitrochlear nodes function in an interval role with the axillary lymph node basin. Therefore we recommend that all patients with a positive epitrochlear SLN undergo completion axillary dissection.