Sentinel lymph node in Merkel cell carcinoma: to biopsy or not to biopsy?

Sentinel lymph node biopsy (SLNB) is commonly recommended for patients with primary Merkel cell carcinoma (MCC). However, it is critically discussed whether survival rates improve by SLNB in MCC patients in general or in subgroups of higher risk (e.g. with primary tumor size >1 cm). The present study correlates clinical data, histology and lymph node status with follow-up and survival data to see if subgroups can be identified for modification of the current recommendations. The medical records of 47 patients with histologically confirmed MCC treated between 1995 and 2010 at a German dermatosurgery department were reviewed. Nineteen patients with excision of the primary tumor and SLNB were compared to 28 patients with excision of the primary tumor but without SLNB. End-points of this study were disease-free survival (DFS) and overall survival (OS). In addition, clinical course was correlated with tumor size and size of safety margin. The group of patients who received SLNB showed a significant advantage in terms of OS (P < 0.05), but not in terms of DFS. Tumors of smaller size were associated with a significantly better DFS and a trend towards better OS. Comparing the groups with different safety margins (1-3 cm), no differences in DFS and OS could be found. Our data support the current recommendation for SLNB in all MCC patients and question the use of extensive safety margins in MCC surgery. Larger prospective multicenter studies with multivariate analysis are needed to confirm whether a prolonged OS is really due to the SLNB procedure or biased by other factors.