Expanding access to cancer care: 10% fluorescein sodium is a practical, low-cost method for intraoperative sentinel lymph node mapping in dogs.

Abstract

OBJECTIVE: To evaluate the feasibility and safety of 10% fluorescein sodium for intraoperative sentinel lymph node (SLN) mapping in dogs with cutaneous or subcutaneous tumors. METHODS: 6 client-owned dogs received ID peritumoral injections of 10% fluorescein sodium diluted 1:120 with sterile saline. Lymphatic pathways and SLNs were visualized by means of blue (450- to 495-nm) and black (345- to 400-nm) light sources. Time to fluorescence, qualitative uptake, and adverse events were recorded. Excised SLNs underwent histopathologic evaluation. RESULTS: Lymphatic tracts were visualized in 5 of 6 dogs (83%; 95% CI, 36% to 100%), and SLNs were identified in all dogs (100%; 95% CI, 54% to 100%). Fluorescent uptake was complete in 4 SLNs (67%; 95% CI, 22% to 96%) and partial in 2 (33%; 95% CI, 4% to 78%). Mean time to lymphatic tract fluorescence was 6.7 ± 6.7 minutes, and mean time to SLN fluorescence was 8.0 ± 6.0 minutes. No adverse events occurred. Histopathology identified metastatic mast cell disease in 4 SLNs (67%; 95% CI, 22% to 96%), classified as HN2 in 2 (33%; 95% CI, 4% to 78%) and HN3 in 2 (33%; 95% CI, 4% to 78%), while reactive changes were observed in 2 SLNs (33%; 95% CI, 4% to 78%). Of 2 second-tier nodes, 1 showed HN2 metastasis and 1 reactive changes. CONCLUSIONS: Based on this preliminary study, 10% fluorescein sodium is a safe, feasible, and accessible method for intraoperative SLN mapping in dogs, providing real-time visualization of lymphatic pathways and lymph nodes. CLINICAL RELEVANCE: This low-cost, accessible technique may facilitate adoption of SLN mapping in general veterinary practice. Further studies are warranted.