Immunophenotype of hairy-cell leukaemia after cold polymerization of methyl-methacrylate embeddings from 50 diagnostic bone marrow biopsies.

Hairy-cell leukaemia may be difficult to diagnose in bone marrow biopsies, especially in the early stages or in its residum after complete clinical remission. To consider the impact of published data on immunophenotyping hairy-cell leukaemias, a total of 50 diagnostic biopsies were systematically analysed with a panel of eight antibodies and compared with cases of chronic lymphatic leukaemia (CLL), 20 follicular centre lymphomas, 20 lympho-plasmacytoid immunocytomas, 10 small-cell T-cell non-Hodgkin lymphomas and 20 cases of benign nodular lymphatic hyperplasia. The panel of eight antibodies comprised DBA44, CD45, CD20, CD45R, CD45RO, CD43 and the CD68 antibodies KP1 and Ki-M1P. The hairy-cell leukaemias were staged histologically into four categories of bone marrow infiltration. DBA44 reacted positively in 47/50 cases. CD45 and the B-cell markers CD20 and CD45R reacted in 49/50 and 43/50 cases, respectively. One CD68 marker, KP1, was positive in 38/50 cases but the other-Ki-M1P-only in 1/50 cases. Chronic lymphatic leukaemia cases, the other B-cell NHLs and lymphatic hyperplasias showed strong positivity for CD20 and CD45R, but only the immunocytomas reacted with DBA44 in 7/20 cases. The T-cell NHLs and hyperplasias showed a strong positivity for the T-cell markers CD45RO and CD43. The CD68-marker Ki-M1P revealed a high specificity since it was negative in all NHLs and positive only in one hairy-cell leukaemia. Methyl-methacrylate embedding of bone marrow biopsies under cold polymerization produces a high quality of histo- and cytomorphology, resulting in greater diagnostic reliability and the detection of low-stage infiltration of hairy-cell leukaemia. DBA44 appears as a highly specific antibody to mark hairy-cells since only immunocytomas reacted positively in a few cases. A small panel of antibodies including DBA44. CD20, CD45R and Ki-M1P may serve to distinguish small-cell. NHL from hairy-cell leukaemia even at an early stage or when there are minimal residual tumour cells.