Background: Diagnosis of primary central nervous system lymphoma (PCNSL) is usually made by identifying malignant lymphocytes in the brain, cerebrospinal fluid (CSF), or vitreous. However, these cells are few and friable, and misdiagnosis can occur, even in properly prepared specimens. Recent data suggest that levels of interleukin 10 (IL-10) are elevated in the serum and vitreous of patients with non-Hodgkin lymphoma; levels of interleukin 6 (IL-6) are elevated in the vitreous of patients with intraocular inflammation unrelated to a malignant neoplasm. We investigated whether PCNSL involving the vitreous or CSF is associated with elevated ratios of IL-10 to IL-6.
Patients: Vitreous specimens were obtained from 5 patients with PCNSL involving the eye and from 13 control patients with intraocular inflammation not related to a malignant neoplasm; CSF specimens were obtained from 11 patients with PCNSL.
Results: Levels of IL-10 exceeded those of IL-6 in all 5 patients with intraocular lymphoma but in none of the 13 patients with uveitis (P < .001). In patients with PCNSL, levels of IL-10 exceeded those of IL-6 in 6 of 11 CSF samples with malignant cells compared with 7 of 53 samples without malignant cells (P = .01). The calculated odds ratio (OR) suggests that the risk for malignant involvement of the CSF is about 8 times higher when IL-10 levels exceed IL-6 levels.
Methods: Levels of IL-10 and IL-6 were determined by enzyme-linked immunosorbent assay in both vitreous and CSF specimens.
Conclusions: The occurrence of PCNSL in the eye was strongly associated with elevated vitreous levels of IL-10 relative to levels of IL-6. Moreover, among patients with diagnosed PCNSL, malignant cells were significantly more likely to be present in CSF when levels of IL-10 exceeded those of IL-6.