Significance of Multiple Nodal Basin Drainage in Truncal Melanoma Patients Undergoing Sentinel Lymph Node Biopsy

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Abstract
Background: Although previous studies have demonstrated that truncal site is associated with an adverse prognosis, explanations for such risk are lacking. In addition, the number of nodal basins as well as the number of lymph nodes containing regional metastases are important prognostic factors in these patients. Because the lymphatic drainage pattern of truncal melanoma often includes more than one basin, we designed a study to evaluate (1) whether patients with multiple nodal basin drainage (MNBD) were at an increased risk of lymph node metastases identified by sentinel lymph node (SLN) biopsy, 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, between 1991 and 1997, were reviewed. All patients underwent preoperative lymphoscintigraphy, which established the number and location of draining nodal basins. Univariate and multivariate analyses of relevant clinicopathological 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 presence of at least one pathologically positive SLN. SLN pathology in one basin 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 nodal metastases in truncal melanoma patients. Because the histological status of an individual basin did not reliably predict the status of the other draining basins in patients with MNBD, it is important to adequately identify and completely assess all nodal basins at risk, as defined by lymphoscintigraphy, in truncal melanoma patients.