Blastic Nkcell Lymphoma

General: Blastic NK-cell lymphoma is a rare neoplasm characterized by a blastoid morphology and tendency to involve the skin and peripheral blood. There may also be systemic nodal involvement.126 128 The cell of origin and most appropriate nomenclature for this neoplasm have been subjects of controversy, and this malignancy is incompletely characterized at present. This neoplasm is classified as a natural killer lymphoma in the WHO system, due largely to the characteristic expression of CD56. More recently, however, studies have suggested this neoplasm is derived from DC2 cells, a type of dendritic cells.129-131

Pathology: In cutaneous blastic NK-cell lymphoma, there is typically a diffuse infiltrate of intermediate-sized cells with dispersed chromatin. In many cases, the tumor cells infiltrate the dermis in a single-file pattern 126,128

Immunophenotype: The neoplastic cells are characteristically positive for CD56, CD4, and CD123. Some cases may be at least partially positive for CD34, TdT, and/or CD68.126 128 Other T-cell associated antigens are typically negative. There is no association with EBV.

Molecular genetics: The T-cell receptor genes are in the germline configuration. Characteristic, recurrent cytogenetic abnormalities have not been identified to date.

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