Evaluation of Serum YKL-40 in Canine Multicentric Lymphoma: Clinical and Diagnostic Implications

YKL-40, a secretory glycoprotein, is known as a prognostic biomarker in human cancers, but its role in canine multicentric lymphoma is not well understood. This study aimed to investigate serum YKL-40 levels in thirty dogs with multicentric lymphoma to determine their prognostic value, association with patient characteristics, and potential to predict chemotherapy response. Serum samples were collected before, during, and after chemotherapy, and YKL-40 level was measured using ELISA. The results showed that the pretreatment serum YKL-40 levels were significantly higher in dogs with multicentric lymphoma (394.0 pg/mL, <i>n =</i> 30) than in healthy controls (218.6 pg/mL, <i>n =</i> 11) (<i>p =</i> 0.012). While a cutoff value of 445.1 pg/mL was observed, further studies are needed to clarify its diagnostic utility. Dogs with clinical stage V had the highest YKL-40 levels (<i>p =</i> 0.027), potentially reflecting disease severity. Furthermore, YKL-40 levels decreased after chemotherapy (<i>p =</i> 0.030). However, YKL-40 levels showed no significant association with progression-free survival (PFS) (HR = 0.93, <i>p =</i> 0.830) or overall survival (OS) (HR = 0.99, <i>p =</i> 0.267). In conclusion, serum YKL-40 levels may potentially detect the disease severity, but its prognostic role remains uncertain. Further studies are required to evaluate serum YKL-40 levels as a potential indicator of treatment response or disease recurrence.