Transected thin melanoma: Implications for sentinel lymph node staging

Background and ObjectivesIndications for sentinel lymph node (SLN) biopsy in patients with thin melanoma (1mm thick) are controversial. We asked whether deep margin (DM) positivity at initial biopsy of thin melanoma is associated with SLN positivity. MethodsCases were identified using prospectively maintained databases at two melanoma centers. Patients who had undergone SLN biopsy for melanoma 1mm were included. DM status was assessed for association with SLN metastasis in univariate and multivariate analyses. Results1413 cases were identified, but only 1129 with known DM status were included. 39% of patients had a positive DM on original biopsy. DM-positive and DM-negative patients did not differ significantly in primary thickness, ulceration, or mitotic activity. DM-positive and DM-negative patients had similar incidence of SLN metastasis (5.7% vs 3.5%; P=0.07). Positive DM was not associated with SLN metastasis on univariate analysis (OR 1.69, 95% CI: 0.95-3.00, P=0.07) or on multivariate analysis adjusted for Breslow depth, Clark level, mitotic rate, and ulceration (OR=1.59, 95% CI: 0.89-2.85; P=0.12). ConclusionsFor patients with thin melanoma, a positive DM on initial biopsy is not associated with risk of SLN metastasis, so DM positivity should not be considered an indication for SLN staging in an otherwise low-risk patient.