b) Leukaemia of NK Cells

NK cell tumours are even rarer than T cell malignancies.

Aggressive NK cell leukaemia

A very rare form of leukaemia that is strongly associated with infection with EBV; about 90% of these malignancies contain the EBV genome in their genetic profile. It is more common in Asian populations. Patients present with fever and malaise; the disease progresses rapidly and survival is less than two months.

Chronic NK cell proliferative disorders

Unlike aggressive NK cell leukaemia, these tumours are characterised by an indolent course and are not considered true leukaemia. The median age of diagnosis is 60. It rarely progresses.