Sentinel Lymph Node Biopsy in Clinically Node‐Negative Merkel Cell Carcinoma: An Update of the Westmead Hospital Experience

BACKGROUND: Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine malignancy with a high risk of nodal metastasis. Sentinel lymph node biopsy (SLNB) is used to stage clinically node-negative disease and to guide adjuvant therapy decisions. This study updates the Westmead Hospital experience with an expanded cohort and extended follow-up. METHODS: Patients with clinically node-negative MCC who underwent SLNB between 1998 and 2024 were identified from an institutional database. Demographic, tumour, treatment and outcome data were reviewed. RESULTS: A total of 75 patients (57 men, 18 women; median age 74 years) underwent SLNB. A total of 28 (37%) had a positive SLNB and 47 (63%) a negative SLNB. Seven patients with a negative SLNB developed nodal recurrence, for a false-negative rate of 20%. Among patients with head and neck primaries, the false-negative rate was 12% (3/31). Overall recurrence occurred in 11 of 47 (23%) SLNB-negative and 11 of 28 (39%) SLNB-positive patients (p = 0.23). Distant recurrence was more frequent after a positive SLNB (18% vs. 6%). Overall survival did not differ significantly by SLNB status (p = 0.11). CONCLUSION: MCC demonstrates a high rate of subclinical nodal metastases, with a SLNB positivity rate of nearly 40% in our series. These findings support the use of SLNB in the management of clinically node-negative MCC to improve staging accuracy, prognostication and guide management decisions, with an acceptable false-negative rate under close surveillance.