Peripheral T‐cell lymphoma with central nervous system involvement and elevated interleukin‐10 levels in the cerebrospinal fluid: A case report

Central nervous system (CNS) involvement in peripheral T‐cell lymphoma (PTCL) is rare and is associated with poor prognosis. This report presents two pathologically confirmed PTCL cases. Although cerebrospinal fluid (CSF) flow cytometry did not detect tumor cells, CSF analysis revealed significantly elevated interleukin (IL)‐10 levels and an increased IL‐10/IL‐6 ratio, suggesting CNS involvement. Following effective chemotherapy, which crossed the blood‐brain barrier, IL‐10 levels and the IL‐10/IL‐6 ratio decreased significantly, with clinical improvement. These findings suggest that IL‐10 is a valuable supplementary diagnostic marker for CNS involvement in PTCL. Whole‐brain radiation therapy, as a consolidative treatment, may be effective for residual or refractory lesions and improve prognosis. We review these patients’ clinical and diagnostic features and discuss the role of radiotherapy in the treatment of CNS involvement in PTCL.