A, For the Glioma Index, samples were divided into training set 1, validation set 1, and the exploratory set. Noncancer control samples were collected from the National Cancer Center Biobank (noncancer 1 controls) and the general population undergoing routine health checkup at a clinic in Yokohama, Japan (noncancer 2 controls). B, For the 3-Tumor Index, samples were divided randomly into 2 groups (4:1, training set 2 and validation set 2) to develop models for discriminating between glioblastoma (GBM), primary central nervous system (CNS) lymphoma (PCNSL), and metastatic brain tumors.