Diagnostic utility of NLR, PLR, and SII for canine mammary gland tumor malignancy

Although histopathological examination remains the gold standard for evaluating the prognosis of canine mammary gland tumors (MGTs), the time required to obtain results limits its utility for immediate postoperative prognostic assessment.Concurrently, cumulative evidence suggests that the evaluation of systemic inflammatory responses correlates with tumor prognosis.This study evaluated whether readily available inflammatory biomarkers, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII), could help predict malignancy in dogs with MGTs.Medical records of 104 dogs diagnosed between January 2018 and June 2024 from five veterinary hospitals were reviewed, including 64 benign MGTs and 40 malignant MGTs.A healthy control group was also included for comparison.Dogs with malignant MGTs had significantly higher neutrophil counts than those with benign MGTs.NLR and SII were also significantly higher in malignant than in benign tumors, whereas PLR did not differ significantly between the two groups.ROC analysis identified an optimal cutoff value of 3.63 for NLR (AUC 0.752; sensitivity 68%; specificity 80%) and 2112.65 for SII (AUC 0.673; sensitivity 43%; specificity 95%) for distinguishing malignant from benign MGTs.These findings suggest a novel and practical bloodbased approach for the preoperative assessment of malignancy in canine MGTs.NLR and SII may serve as useful adjunctive biomarkers, whereas PLR showed limited discriminatory value.However, these markers should be interpreted cautiously, particularly SII because of its relatively low sensitivity.