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Aggressive NK-cell leukemia is characterized by a systemic proliferation of NK cells. This is a disease with an aggressive systemic proliferation of natural killer cells (NK cells) and a rapidly declining clinical course.
Since the number of neoplastic cells in the peripheral blood and marrow can be limited, the disease is different from the usual leukemias and thus has been called aggressive NK-cell leukemia/lymphoma in the past.
The most common sites of involvement are peripheral blood, bone marrow, liver and spleen; however, dissemination to any organ is possible
Overlap with extranodal NK/T-cell lymphoma showing multi-organ involvement may be possible, but it is unclear whether Aggressive NK-cell leukemia represents the leukemic counterpart of extranodal NK/T-cell lymphoma.