Role of sentinel lymph node biopsy in patients with Merkel cell carcinoma: statistical analysis of 403 reported cases

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy with a high rate of nodal metastasis. Sentinel lymph node biopsy (SLNB) is used in MCC and other cancers to identify regional node micrometastases in patients with clinically negative nodes; however, whether SLN status is associated with recurrence or prognosis in MCC is unclear.

A statistical analysis was performed of 397 published cases of MCC with SLNB results from 22 reports and 6 new cases, in order to elucidate any correlation between SLN status and recurrence, and to determine false-negative rates for SLNB.

Of these 403 cases, 128 (31.8 %) had positive SLNs; 16 of these 128 (12.5 %) developed recurrence (6 nodal, 10 distant). Of 275 patients with negative SLNs, 27 (9.8 %) developed recurrence (19 nodal, 8 distant). Patients with positive SLNs had a greater risk of distant metastasis (OR 2.82; P = 0.037; 95 % CI 1.089-7.347). The false-negative rate for SLNB in all 403 patients was 12.9 %. Use of the immunohistochemical approach to diagnosis of micrometastasis with anti-CK20 antibody did not affect the false-negative rate.

Patients with positive SLNs had a greater risk of distant metastasis in MCC; positive SLN was an important prognostic factor in MCC. Further studies using standardized, more-sensitive techniques to examine entire SLNs may decrease the false-negative rate, and improve the significance of SLNB in MCC.