Progressive Disease in Sentinel-negative Melanoma Patients: Biological Differences and Importance of Sentinel Lymph Node Biopsy.

BACKGROUND/AIM: Among the most important prognostic factors in melanoma is the sentinel lymph node (SLN) status. MATERIALS AND METHODS: Using our electronic database we identified 109 of 890 SLN-negative patients with progressive disease (PD). These patients were characterized for melanoma type, molecular type, sequence and extent of metastatic spread. RESULTS: A total of 61 of 109 SLN-negative patients had PD in the SLN-basin indicating false-negative SLN (group-1). Forty eight of 109 patients had PD at distant sites and were therefore impossible to be identified using SLN biopsy (group-2). Despite distant spread these patients had significantly more single organ metastasis (p<0.001) and significantly longer disease-free-survival (p=0.001) compared to group-1. Additionally, to significant differences on a molecular basis between the two groups (p=0.01), all lentigo maligna and spindle-cell-melanomas belonged to group-2 and all, except one lentigo maligna melanoma, had single visceral metastasis. CONCLUSION: Two different biological groups among SLN-negative patients with PD were demonstrated. Extravascular-migratory-metastasis, rather than hematogenous spread, might be responsible for the observed PD with single organ involvement.