Prognostic significance of drainage to pelvic nodes at sentinel lymph node mapping in patients with extremity melanoma.

Patients undergoing sentinel lymph node (SLN) mapping for lower extremity melanoma may have drainage to pelvic nodes (DPN) in addition to superficial inguinal nodes. These nodes are not sampled routinely at SLN biopsy. Factors predicting DPN and its prognostic significance were assessed in a large cohort of patients undergoing an SLN biopsy. Three hundred and twenty five patients with single primary melanomas of the lower extremity or buttocks who underwent SLN mapping were identified from our prospective melanoma database (December 1995-October 2008). Associations of clinical and pathologic factors with DPN and time to melanoma recurrence (TTR) were analyzed by logistic and Cox regression, respectively. DPN was common, occurring in 23% of cases. Increased Breslow's thickness (P=0.007) and age (P=0.01) were associated with DPN by multivariate analysis. Patients with DPN were not more likely to have a positive SLN; however, SLN- patients with DPN showed a shorter TTR (P=0.02) in a multivariable model including thickness and ulceration. With age included in the model, DPN remained marginally associated with TTR in this group (P=0.08). The pelvic recurrence rates observed were similar in recurrent patients with DPN compared with those without DPN (39% in both groups). In conclusion, DPN occurs in almost one-quarter of patients with lower extremity melanoma and is marginally associated with a shorter TTR in SLN- patients.