Significance of multiple nodal basin drainage in truncal melanoma patientsundergoing sentinel lymph node biopsy

Background: Although previous studies have demonstrated that truncal site i s associated with an adverse prognosis, explanations for such risk are lack ing. In addition, the number of nodal basins as well as the number of lymph nodes containing regional metastases are important prognostic factors in t hese patients. Because the lymphatic drainage pattern of truncal melanoma o ften includes more than one basin, we designed a study to evaluate (1) whet her patients with multiple nodal basin drainage (MNBD) were at an increased risk of lymph node metastases identified by sentinel lymph node (SLN) biop sy, and (2) whether the histological status of an individual basin reliably predicted the status of the other draining basins in patients with MNBD. Methods: The records of 295 consecutive truncal melanoma patients who were managed primarily with intraoperative lymphatic mapping and SLN biopsy, bet ween 1991 and 1997, were reviewed. All patients underwent preoperative lymp hoscintigraphy, which established the number and location of draining nodal basins. Univariate and multivariate analyses of relevant clinicopathologic al factors were performed to assess which factors may predict the presence of a pathologically positive SLN. Results: At least one SLN was identified in 281 patients. MNBD was present in 86 (31%) patients, and a pathologically positive SLN was found in 56 (20 %) patients. By multivariate analysis, the presence of MNBD (relative risk = 1.9; P = .03), tumor thickness (P = .007), and tumor ulceration (relative risk = 2.4; P = .01) were significant independent risk factors for the pre sence of at least one pathologically positive SLN. SLN pathology in one bas in did not predict the histology of other basins in 19 (22%) of 86 patients with MNBD. Conclusions: MNBD is independently associated with an increased risk of nod al metastases in truncal melanoma patients. Because the histological status of an individual basin did not reliably predict the status of the other dr aining basins in patients with MNBD, it is important to adequately identify and completely assess all nodal basins at risk, as defined by lymphoscinti graphy, in truncal melanoma patients.