Background: The status of the sentinel lymph node in melanoma is an important prognostic factor. The clinical predictors and implications of false-negative (FN) biopsy remain debatable.
Methods: We compared patients with positive sentinel lymph node biopsy (SNB) [true positive (TP)] and negative SNB with and without regional recurrence [FN, true negative (TN)] from our prospective institutional database.
Results: Among 2986 patients (84 FN, 494 TP, and 2408 TN; median follow-up 93 months), the incidence of FN-SNB was 2.8%. While calculated FN rate was 14.5% [84 FN/(494 TP + 84 FN) × 100], when we accounted for local/in-transit recurrence (LITR) this rate was 8.5% [46 FN/(494 TP + 46 FN) × 100 %]. On multivariate analysis, male gender (OR 2.0, 95% CI 1.1-3.6, p = 0.018), head/neck primaries (OR 2.5, 95% CI 1.3-4.8, p < 0.006), and LITR (OR 3.5, 95% CI 2.1-5.8, p < 0.001) were associated with FN-SNB. Melanoma-specific survival (MSS) for the FN group was similar to the TP group at 5 years (68 vs. 73%, p = 0.539). However, MSS declined more for the FN group with a longer follow up and was significantly worse at 10 years (44 vs. 64%, p < 0.001). On multivariate analysis, FN-SNB was a significant predictor of worse MSS in melanomas <4 mm in Breslow thickness (HR 1.6; 95% CI 1.1-2.5, p = 0.021).
Conclusions: Male gender, LITR, and head and neck tumors were associated with FN-SNB. FN-SNB was an independent predictor of worse MSS in melanomas <4 mm in thickness, but this survival difference did not become apparent until after 5 years of follow-up.