The invention relates to biotechnology, biology, and medicine. Described is a mouse hybridoma YKL-39, clone 1B2 G4, that is a producer of a monoclonal antibody which detects a human cytoplasmic protein YKL-39 through methods of enzyme-linked immunoabsorbent assay, immunocytochemistry, immunohistochemisty, immunoblotting, and immunoflourescence. The hybridoma is produced by immunizing BALB/c mice with a full-length recombinant human YKL-39 protein and subsequently fusing sensitized splenocytes of the immunized mice with sp2/0 mouse myeloma cells using a 50% polyethylene glycol solution with a molecular weight of 1500. The testing of hybrid clones was conducted using the method of enzyme-linked immunoabsorbent assay. The resulting hybridoma secretes a monoclonal antibody, clone 1B2 G4, that is specific toward the human cytoplasmic protein YKL-39. The antibodies produced by the hybridoma could potentially be used for diagnosing glioblastoma.