Increased quantity of tumor-infiltrating FOXP3-positive regulatory T cells is an independent predictor for improved clinical outcome in extranodal NK/T-cell lymphoma

Background: Extranodal natural killer/T-cell lymphoma (NKTCL) is a clinically heterogeneous disease with a poor prognosis, requiring risk-stratified management in affected patients. Recently, tumor microenvironment including regulatory T cells (Tregs) has been implicated as a prognostic marker in certain types of lymphoma. Patients and methods: We collected 64 NKTCL cases and numerically quantified the amount of tumor-infiltrating FOXP3-positive Tregs by automated slide scanning and image analysis program after immunohistochemical staining using anti-FOXP3 antibody. Results: Patients were able to be classified into two end groups by their level of Tregs. Twenty-eight (44%) patients had Tregs