Aggressive NK cell leukaemia

**Definition:** A rare, highly aggressive, Epstein-Barr virus-associated leukaemia, also known as aggressive NK-cell leukaemia/lymphoma; it may represent the leukemic counterpart of nasal type extranodal NK/T-cell lymphomas. It affects primarily teenagers and young adults. It is characterised by the systemic proliferation of NK cells in the peripheral blood, bone marrow, liver, and spleen.