CD11c (LEU-M5) expression characterizes a B-cell chronic
lymphoproliferative disorder with features of both chronic lymphocytic
leukemia and hairy cell leukemia [see comments]
CA Hanson, TE Gribbin, B Schnitzer, JA Schlegelmilch, BS Mitchell and LM Stoolman
Department of Pathology, University of Michigan Medical School, Ann Abor.
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 CD11c (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 CD11c 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
131.0 x 10(9)/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 negative in all cases. Bone marrow biopsies were
available in 8 of 14. Four showed focal nodular infiltrates and two had
diffuse infiltrates similar to CLL; two showed only minimal interstitial
involvement. All cases expressed multiple B-cell markers, and 12 of 14 had
monoclonal surface immunoglobulin. The leukemic cells of all cases strongly
expressed CD11c, while CD5 was expressed in 7 of 14; only 1 of the 14 cases
expressed the lymph node homing receptor, Leu-8. This unique group of
leukemias appears to represent the malignant transformation of lymphocytes
arising from a stage of lymphocyte differentiation between that found in
typical cases of CLL and that of HCL. CD11c is known to have an important
function in cellular adhesion and may be important in determining the
pattern of lymphocyte tissue distribution found in this group of patients.
Volume 76,
Issue 11,
pp. 2360-2367,
12/01/1990
Copyright © 1990 by The American Society of Hematology
