Outcomes of Patients Undergoing Sentinel Lymph Node Biopsy for Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare, cutaneous malignancy with a propensity for nodal metastasis, for which prognostic factors remain poorly characterized.

All patients treated from April 1996 through December 2022 by wide excision and sentinel lymph node (SLN) biopsy for clinically localized MCC at a single institution were included. Logistic regression was used to evaluate factors associated with a positive SLN, recurrence, and disease-specific death (DSD). Cumulative incidence functions estimated recurrence and DSD with death from other causes as a competing risk.

Of 342 patients with MCC, 140 (41%) had a positive SLN. In multivariable analysis, tumor size > 2 cm, lymphovascular invasion (LVI), and more recent diagnosis were significantly associated with a positive SLN. Among the lowest-risk patients (≤ 1 cm tumors and without LVI), 17% had a positive SLN. Most patients (86%) with a positive SLN received further nodal treatment. At 3 years, only 3% of these patients experienced a recurrence within the same nodal basin. A positive SLN was the only factor independently associated with recurrence (39% vs. 12% at 5 years, p < 0.001). The 5-year incidence of DSD was 3.5%, 10%, and 15% (p = 0.002) for patients with stage I, II, and IIIA disease, respectively.

SLN biopsy for patients with MCC is frequently positive, which is associated with increased risk of recurrence and DSD. Even in the absence of identifiable risk factors for SLN metastasis, the SLN positivity rate is > 10%. SLNB appears to inform prognosis in MCC and guides exceptional regional control.