[Phenotypical diagnosis of Japanese chronic lymphocytic leukemia--an international cooperative study based on the French-American-British classification of mature B-cell leukemias].

To better understand the accuracy in the diagnosis of chronic lymphocytic leukemia (CLL) and characterize the clinical features of CLL in Japan, where the disease is extremely rare, an international cooperative study was conducted by hematologists between Japan and UK. Blood and bone marrow films from 36 patients with a possible-diagnosis of CLL were referred to two laboratories of Nagasaki University Hospital (Nagasaki) and Royal Marsden Hospital (London). According to the FAB criteria, typical CLL 16 and CLL/PL 2, a subtype of atypical CLL, were completely accordant in diagnosis. However, phenotypical diagnosis of CLL mixed, the other of atypical CLL, and intermediate lymphocytic leukemia (ILL) in leukemic phase often gave inconsistent results. Especially, 8 cases of atypical CLL designated as likely CLL were equivocal between CLL and ILL, suggesting clinical feature more close to typical CLL than ILL. This indicates the presence of a relatively high incidence of atypical CLL in Japan which dose not exactly fit with the FAB Criteria. Finally, we would like to emphasize that an international cooperative study allows improvement of accuracy in diagnosis and better understanding of the disease entity of lymphoid malignancies, having on ethnically different morbidity.