Primary cutaneous melanoma with regression does not require a lower threshold for sentinel lymph node biopsy.

INTRODUCTION: Histological evidence of primary tumor regression (RG) is observed in 35% or fewer patients with cutaneous melanoma. Some advocate a lower threshold for sentinel lymph node (SLN) biopsy when RG is present.

METHODS: We identified 1,349 patients presenting to our center with clinically localized cutaneous melanoma between 1995 and 2004. Of these, 344 demonstrated histological RG in their primary melanoma. A retrospective analysis of their medical records was performed to obtain clinical and pathological information.

RESULTS: The median Breslow depth for the 344 patients with RG was 1.1 mm versus 1.5 mm for 1,005 patients with no regression (NRG) (P < 0.005). SLN biopsy was performed in 64% of patients with RG and 72% without. Positive SLN was more common in those with NRG than in those with RG (18% vs 10%, P = 0.005). Only one RG patient with thin melanoma (</=1 mm, Clark IV) had a positive SLN. When stratified by Breslow depth, patients with RG had lower rates of SLN positivity in all groups (</=1.0mm, >1.0 and </=2.0mm, >2 and </=4 mm, and >4.0 mm). Recurrence was more common in patients with NRG (21% vs 12%; P < 0.005). Both local and systemic recurrence occurred more commonly in patients with NRG (4% vs 1%, P = 0.002 and 8% vs 3%, P < 0.005, respectively)

CONCLUSIONS: The presence of histological RG in a primary melanoma predicts neither SLN positivity when stratified by Breslow depth nor increased risk of recurrence when compared with melanomas with NRG.