Long-term outcomes and patterns of recurrence in patients with thin melanoma and a negative sentinel lymph node biopsy: a single-center experience

The majority of patients diagnosed with melanoma have thin melanomas (≤1 mm). Data on the rate and pattern of recurrence after a negative sentinel lymph node biopsy (SLNB) are sparse. We retrospectively searched our institutional database and retrieved the records of patients with thin melanomas who underwent an SLNB with negative results. We analyzed patterns of recurrence, time to recurrence, and mode of diagnosis. Thirteen of the 198 patients with thin melanomas and negative SLNB results had tumor recurrence (6.5%): two local in transit (15.4%), three regional (21.3%), and eight distant (61.5%). Distant recurrences tended to occur later than local or regional ones [median disease-free survival = 50 months (95% confidence interval: 36.1-63.9) vs. 34 and 15 months (95% confidence interval: 5.4-24.6), P = 0.005, respectively]. The percentage of patients with tumor thickness ≥0.8 mm was higher among those who sustained recurrence (84.6 vs. 64.9% for no recurrence, P = 0.04). The majority of patients with recurrence were not being followed up when diagnosed (69%), and they are presented because of clinical symptoms. Patients with recurrence had lower survival compared with those without recurrence (median: 118 months vs. ongoing survival, P < 0.001, respectively). Melanoma recurrence in patients with thin melanomas and negative SLNBs is rare, tends to be distant, and negatively affects prognosis. Recurrence tends to occur in patients with melanoma thickness ≥0.8 mm. Further studies are needed to identify patients with high recurrence risk and determine optimal follow-up protocols.