Sentinel node studies in truncal melanoma: does an increased number of draining basins correlate with an increased risk of lymph metastasis?

Objectives: To assess whether an association exists between drainage to multiple basins and lymphatic metastasis in patients with truncal melanoma. Methods: We retrospectively reviewed 227 patients with primary malignant melanoma between January 2006 and December 2009. All patients received an intradermal injection of (99m)Tc-nanocolloid and lymphoscintigraphy followed by sentinel node biopsy. Pre-staging histology with Breslow thickness from excision biopsy was also obtained. Results: 82/227 (36%) patients with primary truncal melanoma were identified. Nodal histology was positive for metastatic disease in 27/82 (32.9%) patients. Of these 27, 15 had 1 basin of drainage, 7 had 2 basins of drainage and 5 had 3 basins of drainage. Of the 55 node-negative patients, 35 had 1 basin, 18 had 2 basins and 2 had 3 basins of drainage. We found no significant correlation with sentinel node positivity and those that had ≥2 drainage basins. Breslow thickness was available in 65/82(79.2%) patients. Sentinel node biopsy was positive in 6/28 patients who had <1.5 mm thickness, 8/14 who had a 1.5–3.9 mm thickness and 9/23 who had ≥4 mm thickness. There was a significant correlation between Breslow thickness of ≥4 mm and nodal positivity (P = 0.03). Conclusion: This study demonstrates no association between multiple drainage basins and sentinel node histology. Sentinel lymph node status did correlate with Breslow thickness.