Prediction of nonsentinel lymph node metastasis in acral melanoma with positive sentinel lymph nodes

Background Metastasis in a nonsentinel lymph node (non‐SLN) is an unfavorable independent prognostic factor in cutaneous melanoma (CM). Recent data did suggest potential value of completion lymph node dissection (CLND) in CM patients with non‐SLN metastasis. Prediction of non‐SLN metastasis assists clinicians in deciding on adjuvant therapy without CLND. We analyzed risk factors and developed a prediction model for non‐SLN status in acral melanoma (AM). Methods This retrospective study enrolled 656 cases of melanoma who underwent sentinel lymph node biopsy at Fudan University Shanghai Cancer Center from 2009 to 2017. We identified 81 SLN + AM patients who underwent CLND. Clinicopathologic data, including SLN tumor burden and non‐SLN status were examined with Cox and Logistics regression models. Results Ulceration, Clark level, number of deposits in the SLN (NumDep) and maximum size of deposits (MaxSize) are independent risk factors associated with non‐SLN metastases. We developed a scoring system that combines ulceration, the cutoff values of Clark level V, MaxSize of 2 mm, and NumDep of 5 to predict non‐SLN metastasis with an efficiency of 85.2% and 100% positive predictive value in the high‐rank group (scores of 17–24). Conclusions A scoring system that included ulceration, Clark level, MaxSize, and NumDep is reliable and effective for predicting non‐SLN metastasis in SLN‐positive AM.