Positive sentinel lymph node biopsy predicts local metastases during the course of disease in Merkel cell carcinoma.

The purpose was to investigate the predictive power of sentinel lymph node biopsy (SLNB) in Merkel cell carcinoma (MCC) patients, using clinical data collected during treatment. The aim was also to review the treatment protocols for MCC patients in Finland. These data were retrieved and compared after identification in the Finnish Cancer Registry from 1979-2009. Hospital files were reviewed for demographic and treatment-related data. Statistical analysis was performed for survival comparing sentinel lymph node positive and negative patients. Specific inclusion criteria yielded a cohort of 33 patient records, which accounted for 15% of the 225 diagnosed MCC patients during the study period. The male:female ratio was 1:1.5. On average, in the lymphoscintigraphy 2 ± 1.62 sentinel lymph nodes visualised and 2 ± 2.4 sentinel lymph nodes were removed in the operation. The mean primary tumour size in sentinel lymph node positive patients was 12.7 mm and in sentinel lymph node negative patients it was 19 mm. Nine patients had micrometastases in their removed sentinel lymph nodes. The patients with positive sentinel lymph node developed local metastases during the course of disease more often than sentinel lymph node negative patients (p < 0.003). However, there was no statistical difference in overall survival in sentinel lymph node negative and positive patients (p > 0.12). This study emphasises that SLNB appears to be a useful tool in determining the stage of MCC patients regardless of tumour size. A positive sentinel lymph node predicts the metastatic course of disease.