Sentinel lymph node biopsy in patients with Merkel cell carcinoma: An emerging role and the Westmead hospital experience

Background: Merkel cell carcinoma (MCC) is an aggressive cutaneous malignancy which has a high rate of nodal metastasis. Sentinel lymph node biopsy (SLNB) enables the identification of occult nodal metastases. We sought to calculate the rates of positive and false negative SLNB and to evaluate the impact of SLNB on the staging and management of patients with MCC at our institution. Methods: A total of 16 patients with stage I or II MCC who had undergone SLNB were identified from a prospectively maintained database of 114 patients with MCC who presented to Westmead Hospital, Sydney, Australia between 2000 and 2010. Data on patient characteristics, tumour and treatment details and patient follow up were extracted from a computer database and patient medical records. Results: Eight patients (50%) had a positive SLNB and eight had a negative SLNB. The median follow up from diagnosis was 19.5 months (range 4-40) with most patients (69%) alive without evidence of disease at the time of last follow up. All eight patients with a positive SLNB subsequently underwent nodal treatment. This consisted of radiotherapy in five and completion lymphadenectomy and adjuvant radiotherapy in three. None of the eight patients who had a negative SLNB underwent any nodal treatment following SLNB. Two of these patients developed nodal relapse, giving a false negative rate of 20%. Conclusion: Half of our patients were upstaged and underwent nodal treatment as a result of their SLNB. Given the high rate of SLNB positivity, we believe that SLNB has a role in the management of MCC. As there is a risk of a false negative SLNB, close observation of the regional nodal basins is warranted in patients who have had a negative SLNB. Further studies are required to investigate the impact of SLNB on survival.