DIAGNOSTIC RELEVANCE OF PERIPHERAL-BLOOD IMMUNOCYTOCHEMISTRY IN HAIRY-CELL LEUKEMIA

Aims-(1) To assess the diagnostic relevance of peripheral blood immuno cytochemistry in hairy cell leukaemia (HCL); (2) to compare the immuno staining of bone marrow biopsy specimens with bone marrow and peripher al blood cytospins; (3) to evaluate the sensitivity of the different m arkers used; (4) to identify the ultrastructural localisation of DBA.4 4 in HCL variant. Methods-Immunoenzymatic staining procedures, immunop eroxidase and immunoalkaline phosphatase, were used with a panel of mo noclonal antibodies directed to HCL associated antigens. Ultrastructur al immunostaining was performed using colloidal gold conjugated antibo dies. Results-HCL showed strong cytoplasmic reactivity for CD22, CD25, CD103, DBA.44, kappa, or lambda light chains. Peripheral blood diagno stic hairy cells were found in all the cases with absolute counts rang ing from 0.11 x 10(9)/l up to 6.4 x 10(9)/l and values increasing with the size of the spleen. A median of 36.5% of leukaemic cells was foun d in bone marrow aspirates and 70% in bone marrow trephine specimens. The monoclonal antibodies CD22 and DBA.44 showed the highest and the l owest percentage of positive hairy cells, respectively; this differenc e was statistically significant (p = 0.0025). Ultrastructural immunola belling with DBA.44 showed a cytoplasmic membrane localisation of the antigen in one case of HCL variant. Conclusions-(1) Immunocytochemistr y is a useful technique which enhances the accuracy of diagnosis in HC L; (2) peripheral blood immunocytochemistry is recommended because it highlights hairy Methods cells in all cases; (3) CD22 appears to be MA TERIALS the most sensitive of the markers tested; (4) ultrastructural analysis is a useful tool in selected cases of HCL variant.