Analysis of chronic lymphoid leukaemias according to FAB.

We have studied the immunophenotypic features in patients with chronic lymphoid leukaemia and investigated the suitability of classification according to guidelines of the French-American-British (FAB) group. Immunophenotyping was carried out on cytocentrifuge preparations of mononuclear blood leukocytes using the alkaline phosphatase-antialkaline phosphatase (APAAP) method. The 114 leukaemias, including 58 cases of B-chronic lymphocytic leukaemia (B-CLL), 3 Waldenström's macroglobulinaemia, 6 prolymphocytic leukaemia (B-PL), 13 B-CLL/PL, 4 B-CLL of mixed cell type, 8 splenic lymphoma with villous lymphocytes (SLVL), 8 hairy cell leukaemia (HCL), two HCL variant, three leukaemic phase of follicular lymphoma, two leukaemic phase of intermediate lymphoma, two plasma cell leukaemia and two chronic T-cell leukaemia, were investigated. The 111 of 112 B-chronic lymphoid leukaemias (B-CLL + B-PL + B-CLL/PL + SLVL + HCL etc.) showed monotypic light chains. The antibody HML1 was highly specific for HCL. The antibodies CD11c and CD25 were positive in all HCL cases, but were not specific for this disease. CD5 positivity and CD22s negativity were found in most patients with B-CLL, B-CLL/PL and B-CLL of mixed type. This marker type has a limited value for differentiation from the other chronic lymphoid leukaemias. We also studied three patients with chronic lymphoid leukaemia which were not described by the FAB classification. We conclude that a study of the morphology of the leukaemic cells was the most useful basis for the diagnosis of these leukaemias, whereas immunotyping was apparently valuable only in individual cases.