JSH practical guidelines for hematological malignancies, 2018: II. Lymphoma-9. Extranodal NK/T-cell lymphoma, nasal type (ENKL)
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The 2017 WHO Classification lists three entities under natural killer (NK) cell neoplasms: extranodal NK/T-cell lymphoma, nasal type (ENKL); aggressive NK-cell leukemia (ANKL); and chronic lymphoproliferative disorders of NK cells (CLPD-NK) . All entities are rare, but the incidence of ANKL is less than one-seventh that of ENKL , therefore, there is little evidence regarding its treatment. Consequently, this chapter only covers ENKL.
ENKL is almost always derived from NK cells, but a small number of cases that originate in or around the nasal cavity (hereafter collectively referred to as nasal ENKL) are considered to be lymphomas derived from T cells. As it is not possible to differentiate between the NK- and T-cell types with current histopathological methods, which use formalin-fixed paraffin-embedded material, the entity is described as NK/T-cell lymphoma. However, as it is possible to differentiate between the NK- and T-cell types with flow cytometry or genetic...