Morphological and Immunophenotypical Characterization of Japanese B-Cell Lymphocytic Leukemia

Abstract

We have analyzed the clinical and laboratory features of 42 patients with B-cell leukemia. Based on the FAB criteria, the cases were classified in 3 groups: I) typical CLL 15, II) atypical CLL 9 which included 6 cases with large cells, and III) B-cell lymphoma in leukemic phase 18. Cases diagnosed as typical CLL (group I) had similar features to those seen in CLL patients from Western countries. The morphology and markers in cases from group III corresponded to B-cell lymphoma in leukemic phase. On the other hand, group II included 3 cases classified as atypical CLL according to FAB criteria. 1 CLL/PL and 2 mixed CLL and 6 cases with rather distinct features, namely: 1) lymphocytosis (42 ± 41 × 10⁹/1 in average) with large mature-looking lymphocytes with abundant cytoplasm: 2) an immunological profile consistent with CLL but, in addition with the consistent expression of CD38; 3) absence of a monoclonal band in the serum and 4) a clinical course and prognosis similar to CLL. Our findings suggest the existence of a B-cell disorder in Japan very close to CLL but distinct from typical and atypical CLL as seen in Western countries. Further studies would clarify whether such an entity is exclusively confined to Japan having a distinct natural history.

Key Words:

• chronic lymphocytic leukemia (CLL)
• atypical CLL
• phenotype CD5⁺ B cell
• FAB criteria