Aggressive NK-cell leukemia
|Aggressive NK-cell leukemia|
|Classification and external resources|
It is also called aggressive NK-cell lymphoma, or large granular lymphocyte leukemia, NK-cell type
This rare form a leukemia is more common among Asians in comparison to other ethnic groups. It is typically diagnosed in adolescents and young adults, with a slight predominance in males.   
Clinical features 
This disease has a strong association with the Epstein-Barr virus (EBV), but the true pathogenesis of this disease has yet to be described. The cell of origin is believed to be an NK cell. Blastoid NK cell lymphoma appears to be a different entity and shows no association with EBV.
Patients usually present with constitutional symptoms (malaise, weight loss, fatigue), and hepatosplenomegaly is commonly found on physical exam. Lymphadenopathy is also found to a lesser extent. Due to the aggressive nature of the disease, patients may initially present at a more advanced stage, with coagulopathies, hemophagocytic syndrome, and multi-organ failure.  
Laboratory findings 
Sites of involvement 
Peripheral blood 
The leukemic cells have a diameter mildly greater than a large granular lymphocyte (LGL) and have azurophilic granules and nucleoli of varying prominence. Nuclei may be irregular and hyperchromatic.
Bone marrow 
Bone marrow involvement runs the spectrum between an inconspicuous infiltrate to extensive marrow replacement by leukemic cells. Reactive histiocytes displaying hemophagocytosis can been seen interspersed in the neoplastic infiltrate.
Other organs 
Leukemic involvement of organs is typically destructive on tissue sections with necrosis and possibly angioinvasion, and the monotonous infiltrate may be diffuse or patchy.
Molecular findings 
|Positive||CD2, CD3ε, CD56, perforin, granzyme B, TIA-1, CCR5|
Genetic findings 
Due to the NK lineage, clonal rearrangements of lymphoid (T cell receptor; B cell receptor) genes are not seen. The genome of the Epstein Barr virus (EBV) is detected in many cases, along with a variety of chromosomal abnormalities.
Currently Aggressive NK-cell leukemia, being a subtype of PTCL, is treated similarly to B-cell lymphomas. However, in recent years, scientists have developed techniques to better recognize the different types of lymphomas, such as PTCL. It is now understood that PTCL behaves differently from B-cell lymphomas and therapies are being developed that specifically target these types of lymphoma. Currently, however, there are no therapies approved by the U.S. Food and Drug Administration (FDA) specifically for PTCL. Anthracycline-containing chemotherapy regimens are commonly offered as the initial therapy. Some patients may receive a stem cell transplant. Novel approaches to the treatment of PTCL in the relapsed or refractory setting are under investigation.
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