Aggressive acute CD3+, CD56- T cell large granular lymphocyte leukemia with two stages of maturation arrest.

In the majority of clonal expansions of CD3+ large granular lymphocytes (LGL), referred to as T-LGL leukemia, patients have a chronic disease, often manifested by severe neutropenia, rheumatoid arthritis, and mild to moderate splenomegaly. The characteristic leukemic phenotype is CD3+, CD8+, CD16+, CD57+ and CD56-. Here we report an unusual case of T-LGL (CD3cyt+, CD3surface-, CD16+, CD56-) with clinicopathological features (acute presentation, large tumor mass, and systemic illness with highLGL counts at diagnosis) similar to those described for patients with CD3-natural killer (NK)-LGL leukemia. Two distinct stages of maturation arrest were observed: in the lymph node abnormal cells were CD4+, CD8+ whereas the majority of circulating leukemic cells expressed only CD8. TCR gamma (TCR gamma) gene configuration demonstrated that these originated from the same T cell clone, suggesting a maturation process between the two populations, or preferential passage of CD8 single positive cells into the blood.