[Hairy cell leukemia. I.--Clinical, biological and evolutive study on twenty-eight cases (author's transl)].

A clinical and laboratory evaluation of 28 patients with hairy cells leukemia is performed. Twenty-two had splenomegaly and all but one had a pancytopenia with 5 to 70% of hairy cells in blood. A tartrate-resistant acid phosphatase activity was positive in the hairy cells of 11 patients of 14 studied. In all patients a myelofibrosis and a leukemic infiltration were found in a bone-marrow biopsy of iliac crest. Hemodilution by splenomegaly, mild hemolysis and dyshematopoiesis were observed in 10 patients by a 51Cr or 59Fe isotopic exploration. In seven cases an immunological study of the hairy cells was performed, a high percentage of the leukemic cells of these 7 patients had polyclonal surface Ig but without resynthesis of monoclonal S Ig which is a feature usually associated with B lymphocytes. In the blood of these patients normal T and B lymphocytes were decreased. A splenectomy was done in 12 patients (43%) always for severe pancytopenia Splenectomy was not randomised. Spleen weights ranged from 1 085 to 3 600 g. In splenectomised patients the level of hemoglobin, segmented cells and thrombocytes was significantly higher after surgery. The survival rate is better in the splenectomised group (median survival 57 months) than in the non-splenectomised group (median survival 19 months). Infectious diseases were frequent in all patients but less after splenectomy. Fourteen patients died, 8 owing to pancytopenia.