HAIRY-CELL LEUKEMIA - AN ULTRASTRUCTURAL-STUDY OF HAIRY-CELLS BEFORE AND AFTER INTERFERON THERAPY

Aims and background: To test the diagnostic relevance of the presence of ribosome-lamellae complexes (RLC) in 18 hairy cell leukemia (HCL) c ases, and to correlate clinical response to interferon (IFN) therapy w ith hairy cell ultrastructural modifications in 5 of these cases. Meth ods: Peripheral blood samples of 18 HCL patients were studied by trans mission electron microscopy, Five of these patients received IFN treat ment and subsequently were evaluated at different intervals for ultras tructural modifications of the peripheral blood, Results: RLC were obs erved in 66.66% of our 18 HCL patients, but in less than 1% of all the cases contained in the files (consisting of over 8,000 cases) of our Electron Microscopy Unit. The microvilli disappeared after IFN therapy in the patients who did not display RLC before therapy (2 cases), whe re as they were fewer, shortened and blunted, but still evident, in th e cases where RLC had been observed before therapy (3 cases). Moreover , in the HCL cases with pretherapy RLC, neoplastic cells still synthes ized RLC after IFN treatment, but their morphologic aspect was immatur e, Conclusions: Our study suggests that: 1) the presence of RLC, when associated to the hairy aspect of the cells, has considerable diagnost ic value even though RLC are observed in other rare neoplastic and non -neoplastic conditions; 2) HCL cases with pre-therapy RLC exhibited a morphologic response to IFN therapy different from that of cases witho ut pre-therapy RLC; 3) the quantitative and qualitative modifications of RLC following IFN treatment, as yet unexplained, are probably relat ed to IFN action, in line with a previous report.