Agranular CD4+/CD56+ hematodermic neoplasm: a distinct entity described in the recent World Health Organization-European Organization for Research and Treatment of Cancer classification for cutaneous lymphomas.

Agranular CD4+/CD56+ hematodermic neoplasm is a distinct form of lymphoma with aggressive behavior and marked predilection for cutaneous involvement. Because of CD56 positivity, natural killer cells were initially suggested as the cell of origin in this tumor. In the recent World Health Organization-European Organization for Research and Treatment of Cancer classification, the term blastic natural killer cell lymphoma has been replaced with CD4+/CD56+ hematodermic neoplasm because of its derivation from a plasmacytoid dendritic cell precursor. Clinicopathologic features, immunohistochemical features, and differential diagnosis of this rare neoplasm with emphasis on the recent World Health Organization-European Organization for Research and Treatment of Cancer classification are discussed.