Lymphomatous features of aggressive NK cell leukaemia/lymphoma with massive necrosis, haemophagocytosis and EB virus infection

Aims: Aggressive natural killer (NK) cell leukaemia will be categorized as a distinct entity in the new WHO classification of malignant lymphomas. However, its non-leukaemic features remain unclear. We therefore investigated the morphological and immunophenotypic features of this lymphoma. Methods and results: Four cases with aggressive NK cell lymphoma were morphologically and immunohistochemically studied. All cases followed an aggressive course with death occurring within about 3 months of initial presentation, In these cases, the neoplastic cells disseminated throughout systemic lymph nodes and invaded various tissues and organs. The lymphoma cells were large cells showing nuclear irregularity and a pattern of sinusoidal invasion in lymph nodes. Apoptosis and coagulation necrosis were both frequently observed. Haemophagocytosis was observed in all cases. Neoplastic cells in paraffin-embedded tissue specimens from these patients-had CD3(CD3 epsilon)(+) CD56(123C3)(+) granzyme(+) TIA-1(+) EBERT+ CD43(MT1)(-) CD45RO(UCHL-1)(-) CD57(Leu7)(-) CD20(L2 6)(-) phenotypes, In the two cases where tissue was available for immunohistochemical study in frozen sections, neoplastic cells showed CD56(Leu19)(+) perforin(+) Fas ligand(FasL)(+) CD2(Leu5b)(-) CD3(Leu4)(-) CD4(Leu3)(-) CD5(Leu1)(-) CD7(Leu9)(-) CD8(Leu2)(-) beta F1(-) TCR delta1(-) phenotypes, CD16(Leu11b) was positive in one case. Conclusions: Natural killer cell lymphomas appear to represent a non-leukaemic counterpart of aggressive natural killer cell leukaemia, a relationship similar to that in adult T-cell leukaemia/lymphoma. Awareness and diagnosis of this aggressive lymphoma is important because of its fulminant course.