Reliability and Safety of 1% Methylene Blue for Sentinel Lymph Node Localisation: A Prospective Study

Abstract

Aim: The present study evaluates the feasibility and diagnostic performance of 1% methylene blue dye for sentinel lymph node localisation in patients with clinically node-negative early-stage breast cancer. Study Design: Hospital-based prospective study. Place and Duration of Study: Department of Surgery, SGRDIMSR, Amritsar, from July 2024 to December 2025. Methodology: This prospective study included 69 female patients aged 25 years and above with operable early-stage breast cancer classified as T1-T2 and clinically node-negative. Patients underwent sentinel lymph node mapping using 2-5 ml of 1% methylene blue dye injected intradermally or subdermally in the peritumoral region, followed by sentinel lymph node identification and excision. Histopathological findings from sentinel lymph nodes were compared with final axillary lymph node status. Diagnostic performance was assessed using sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, false-negative rate, and false-positive rate. Results: Sentinel lymph node identification was successful in 66 of 69 patients, giving an identification rate of 95.6%. The largest age group was 41-50 years, comprising 24 patients (34.78%). Invasive ductal carcinoma was the most frequent histological subtype, observed in 56 patients (81.16%), and most tumours were T2 lesions, reported in 56 patients (81.15%). Among the 66 evaluable patients, sentinel lymph node status correctly predicted axillary nodal status in 48 cases. Sensitivity was 77.42%, specificity was 68.57%, positive predictive value was 68.57%, negative predictive value was 77.42%, and overall diagnostic accuracy was 72.73%. The false-negative rate was 22.58%. Conclusion: Methylene blue dye demonstrated a high sentinel lymph node identification rate in clinically node-negative early breast cancer. However, the observed false-negative rate indicates that negative sentinel lymph node findings should be interpreted cautiously. Larger comparative studies are needed to further evaluate its clinical utility.