Gentian violet compared with methylene blue for sentinel lymph node biopsy in breast cancer: A retrospective analysis from a resource-limited setting.

1604 Background: Sentinel lymph node biopsy (SLNB) minimizes morbidity in breast cancer surgeries compared to axillary lymph node dissection. Standard tracers like vital blue (VB), methylene blue (MB) and radioisotopes (RI) are effective but often costly and logistically challenging in low- and middle-income countries (LMICs). Gentian violet (GV), a low-cost alternative, offers potential for resource-constrained settings. Methods: A retrospective cohort study was conducted at Cancer Foundation Hospital Karachi, Pakistan between January 2023 - December 2024. The study included 28 patients with breast cancer who underwent SLNB using GV and RI. Sentinel lymph node (SLN) detection rates, concordance between GV and RI, and safety profiles were assessed. Detection was analyzed across tumor grades, histology, receptor statuses, and neoadjuvant chemotherapy (NACT) status. Results: The majority of patients were aged 41–50 years (n = 8) and > 70 years (n = 8) and had a BMI in the range of 21–30. Tumor size analysis revealed that T2 tumors were most common (57.1%, n = 16), followed by T3 tumors (21.4%, n = 6). Neoadjuvant chemotherapy (NACT) was administered to 35.7% (n = 10) of patients and all patients were clinically node-negative (cN0) at diagnosis with no distant metastases. Stage II disease predominated (78.6%, n = 22), and invasive ductal carcinoma (IDC) was the most common type (71.4%, n = 20), and 53.6% (n = 15) of tumors were poorly differentiated (Grade 3). Receptor status analysis showed ER/PR positivity in 64.3% (n = 18) of cases, triple positivity in 21.4% (n = 6), while HER2/neu-positive and triple-negative subtypes each accounted for 7.1% (n = 2). GV successfully identified SLNs in 96.4% of cases, with moderate concordance with RI (Kappa = 0.512). GV identified more nodes in 32.1% of patients, while RI identified more in 14.3%; both identified the same number in 50%. The false-negative rate for GV was low (4.2%). Detection rates were consistent across histological types (e.g., invasive ductal carcinoma: 1.94 nodes by GV vs. RI), tumor grades (Grade 3: 1.78 by both), and receptor statuses (triple-positive cases: ~2.4 nodes by GV vs. 2 by RI), with no significant differences. NACT did not impact SLN detection (p = 0.844). No complications or adverse events related to GV dye were observed intraoperatively or during the postoperative follow-up at days 0, 3–7, and 30. The safety profile of GV dye demonstrated no staining-related complications, dermatitis, tattooing, or skin necrosis. Conclusions: Gentian violet is a safe, effective, and affordable alternative to MB/VB for SLNB in breast cancer. It demonstrates high detection rates and a favorable safety profile, making it particularly suitable for LMICs. Broader studies are encouraged to validate these findings and further its clinical adoption.