Clinical and Biological Cohort Study of EBV-Positive T/NK-Cell Lymphoproliferative Diseases

This is a multicenter, non-interventional, ambidirectional cohort study of Epstein-Barr virus-positive T/NK-cell lymphoproliferative diseases. The study consists of a retrospective clinical cohort of 500 consecutively diagnosed patients with extranodal NK/T-cell lymphoma and a prospective clinical-biological cohort of 1,000 newly diagnosed patients with extranodal NK/T-cell lymphoma, aggressive NK-cell leukemia, systemic chronic active Epstein-Barr virus disease of T/NK-cell type, or Epstein-Barr virus-positive nodal T/NK-cell lymphoma. The study will characterize clinical features, treatment pathways, response, relapse or progression patterns, and long-term survival. The prospective cohort will additionally undergo standardized collection of peripheral blood and optional tumor tissue specimens at predefined clinical time points. Clinical, molecular, viral, and immune biomarkers will be evaluated for their associations with treatment response, treatment failure, disease progression, and survival. No treatment is assigned by the study.