CD 1 IC ( LEU - M 5 ) Expression Characterizes a B - Cell Chronic Lymphoproliferative Disorder With Features of Both Chronic Lymphocytic Leukemia and Hairy Cell Leukemia

Chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) are two common chronic lymphoproliferative disorders, each having characteristic clinical, morphologic, and immunologic features. Phenotypically, CD5 reactivity in CLL and C D l l c (Leu-M5) reactivity in HCL have characterized these two leukemias among B-cell disorders. In this study, we report 14 cases of a novel chronic lymphoproliferative disorder characterized by lymphocytosis and C D l l c expression, but morphologically similar to CLL. The patients’ ages ranged from 46 to 81 years (median 62). Eleven had palpable splenomegaly, five with markedly enlarged spleens: only one patient had generalized lymphadenopathy. The white blood cell count ranged from 5.2 to 131 .O x 10s/L (median 20.8). The morphologic diagnosis in all cases was CLL, with the cells usually having abundant cytoplasm. No morphologic features of hairy cells were evident; tartrate-resistant acid phosphatase cytochemistry was