Monarch Disease Ontology entry MONDO_0019470 (aggressive NK-cell leukemia) is a rare, highly aggressive, Epstein-Barr virus-associated leukemia, also known as aggressive NK-cell leukemia/lymphoma; it may represent the leukemic counterpart of nasal type extranodal NK/T-cell lymphomas. It affects primarily teenagers and young adults. It is characterized by the systemic proliferation of NK cells in the peripheral blood, bone marrow, liver, and spleen. Also known as: ANKCL, NK cell leukaemia, NK cell leukemia, NK-cell LGL leukaemia, NK-cell LGL leukemia, NK-cell large granular lymphocyte leukaemia, NK-cell large granular lymphocyte leukemia, NK-cell leukaemia.