Diagnostic Accuracy and Predictive Factors of Sentinel Lymph Node Biopsy in Cutaneous Squamous Cell Carcinoma: A Systematic Review.

INTRODUCTION

Sentinel lymph node biopsy (SLNB) is increasingly used to stage cutaneous squamous cell carcinoma (cSCC), particularly in high-risk cases, though its diagnostic accuracy remains debated. This systematic review aims to evaluate SLNB detection rates, diagnostic accuracy, complications and predictors of positivity in patients with non-mucosal cSCC.

METHODS

Following PRISMA guidelines, Medline, Embase, Scopus and Cochrane Library were searched to January 2025. Studies reporting SLNB outcomes in histologically confirmed cSCC were included. Pediatric and mucosal/anogenital cases were excluded. Data on demographics, tumour characteristics, SLNB outcomes and complications were extracted. Comparisons between SLNB-positive, negative and false-negative groups were performed (p < 0.05).

RESULTS

Forty-four studies (3043 patients, 3050 lesions) were included. Among 2956 patients undergoing SLNB, nodes were identified in 96.9%, with positivity in 10.9%. False negatives occurred in 1.7% of the cases (rate 13.2%). SLNB-positive patients had larger tumours (4.24 vs 2.88 cm, p < 0.0001) and deeper invasion (9.81 vs 4.75 mm, p = 0.0007), higher rates of perineural invasion (p = 0.0436), poor differentiation (p = 0.009) and more T2 disease (p = 0.04). No significant differences were found for sex (p = 0.5), immunosuppression (p = 0.068) or tumour location (p = 0.1), though immunosuppression was more prevalent in SLNB-positive cases. Recurrence (24.3% vs 4.2%) and disease-specific mortality (18.2% vs 3.7%) were higher in SLNB-positive patients (p < 0.0002). Complication rates were low (3.2%).

CONCLUSION

SLNB demonstrates high detection but notable false negative rates in cSCC. Positive SLNB correlates with aggressive tumour features and worse outcomes. SLNB may assist staging in high-risk patients but should be used selectively, with close surveillance in SLNB-negative cases.