hairy-cell leukemia [AS, haer + L, cella, storeroom; Gk, leukos, white, haima, blood] , an uncommon neoplasm of blood-forming tissues, characterized by pancytopenia, enlargement of the spleen, and many fine projections on the surface of reticulum cells in the blood and bone marrow. The disease occurs six times more frequently in men than in women and usually appears in the fifth decade with an insidious onset and a variable course marked by anemia, thrombocytopenia, and spontaneous bruising. Some cases may achieve long-term remission through alpha-interferon administration or chemotherapy using vincristine and prednisone. Also called leukemic reticuloendotheliosis.