Results of Sentinel Lymph Node Biopsy in Patients With Thin Melanoma

Abstract

Sentinel lymph node (SLN) biopsy has been shown to be a highly accurate method of staging nodal basins in melanoma patients. Although this technique is widely accepted in patients with intermediate-thickness tumors, it is unclear what the indications are for thin (< or = 1 mm) melanoma. From May 1991 to October 2004, 223 patients with thin melanoma underwent SLN biopsy at Memorial Sloan-Kettering Cancer Center. Most patients with thin melanoma were selected for the procedure because of high-risk clinicopathologic features. Nodal metastases were found in eight patients (3.6%) who underwent SLN biopsy. All positive SLNs were found in patients with > or = .75 mm-thick and Clark level IV melanoma (8 of 114; 7%). Age, sex, tumor location, thickness, Clark level, ulceration, regression, tumor-infiltrating lymphocytes, mitotic rate, and number of mapped nodal basins were not predictive of positive SLNs (chi(2); P = not significant). With a median follow-up of 25 months, there have been no recurrences or deaths in patients with melanoma < .75 mm. Six patients have had regional and/or systemic recurrences (2.7%), only one of whom had a positive SLN. Three patients have died of melanoma; all had negative SLNs. Nodal metastasis in thin melanoma is uncommon, especially in patients with < .75 mm and Clark level II or III melanoma. In our experience, no single clinicopathologic factor was predictive of nodal metastases. The prognostic implications of positive SLNs in thin melanoma remain undefined.