Siglec-15 expression in diffuse glioma and its correlation with MRI morphologic features and ADC

Objective: To investigate the expression of sialic acid-binding immunoglobulin-like lectin 15 (Siglec-15) in diffuse glioma and its correlation with magnetic resonance imaging (MRI) features for glioma patients. Materials and Methods: This retrospective study included 57 glioma patients. Morphological MRI features including the largest tumor diameter, enhancement category, location, calcification, cysts, and hemorrhage were visually rated. Apparent diffusion coefficient (ADC) values were calculated in tumor region. The difference of MRI morphologic features and ADC were compared between patients with positive and negative Siglec-15 expression. Receiver operating characteristic (ROC) curves were further constructed to assess the diagnostic performance. Results: Siglec-15 was not expressed in glioma cells, but in immunocytes such as macrophages in the peritumoral area. Positive Siglec-15 expression was observed in 35.09% (20/57) of patients, and higher in IDH1-mutant gliomas and lower-grade gliomas. The tumor diameter was significantly smaller in patients with positive Siglec-15 expression than in those with negative expression for all glioma patients (p=0.017) and for patients with mutant IDH1 glioma (p=0.020). Moreover, ADC values of the tumor were significantly higher in patients with positive Siglec-15 expression than in those with negative expression for all glioma patients (p=0.027). The areas under curve (AUCs) of the diameter and ADC were 0.702 and 0.686, respectively. A combination of these two parameters generated an improved AUC of 0.762, a sensitivity of 73.68%, and a specificity of 71.87%. Conclusions: Siglec-15 was not expressed in glioma cells, but in immunocytes such as macrophages in the peritumoral area, with a positive rate of 35.09%. Positive Siglec-15 expression in diffuse glioma was correlated with smaller tumor size and higher ADC values.