Hairy cell leukemia: an unusual lymphoproliferative disease: a study of 24 patients.

A laboratory and clinical evaluation of 24 patients with hairy cell leukemia was carried out over a 23-month period. Most patients had splenomegaly without adenopathy or pancyotpenia. Nine of the patients had undergone splenectomy prior to referral; their median WBC count was 6600/mm3. The median WBC count for the 14 patients who had no prior therapy was 3550/mm3, and their median platelet count was 80,500/mm3. Spleen weights ranged from 618 to 3780 g; there appeared to be no relationship between the size of the spleen and the response in the blood counts after splenectomy. Four patients in whom the majority of the WBC were hairy cells underwent splenectomy, which produced no real change in their WBC count; however, there was improvement in the platelet count in three. In contrast, the presence of leukopenia with a low percentage of hairy cells predicted a beneficial response to splenectomy. The study of surface immunoglobulins (SIg) in 16 patients demonstrated that resynthesis had occurred in each case. Phagocytosis of zymosan was studied in 15 patients; in 8 of these, 25% or more of the hair cells were capable of phagocytosis; in 6 others, 0--9%; and in one, 13%. The resynthesis of SIg is a feature usually associated with B-lymphocytes, but the phagocytosis of zymosan is not. Thus, the existence of either a spectrum of functional capabilities of hairy cells or several distinct subtypes is suggested by these data. Platelet aggregation with epinephrine was abnormal in 7 of 14 patients studied but there were no clinically significant bleeding problems. A chromosome abnormality was present in 2 of the 19 patients from whom adequate samples were obtained; the abnormality probably involved chromsome 12 in both patients as well as absent Y and was associated with a rapidly progressive clinical course. The presence of a predominant number of hairy cells with a normal or increased peripheral blood WBC count or of a chromosomal abnormality suggests that splenectomy might not be beneficial as the initial therapy and that chemotherapy should be considered.