T cell prolymphocytic leukemia. 2 cases having a postthymic helper phenotype with complement receptors and 14q+...

We describe 2 elderly patients with splenomegaly and progressive bone marrow failure due to infiltration by leukemic prolymphocytes with a single prominent nucleolus. In each case the leukemia cells had a unique helper T cell phenotype with complement receptors and contained coarse blocks of acid alpha-naphthyl butyrate. A 14q+ chromosome was among the abnormalities that marked one abnormal T cell clone. Histology of the spleen showed mainly red pulp infiltration merging with periarteriolar regions and different from the pseudonodular pattern described in many cases of B cell prolymphocytic leukemia (PLL). Ultrastructurally, leukemia cells contained dense lysosomes, perinuclear clusters of 10-nm microfilaments but no distinctive cytoplasmic inclusions previously described in (B cell) PLL. We suggest that early phenotyping of leukemia cells may enable consideration of monoclonal antibody therapy in elderly patients with bone marrow failure resistant to chemotherapy.