IDENTIFICATION OF A PURE SPLENIC FORM OF CHRONIC LYMPHOCYTIC-LEUKEMIA

A new staging system is proposed for chronic lymphocytic leukemia (CLL) in which patients with isolated splenomegaly are classified into a distinct stage (stage II). Twenty-three such patients (from 2 institutions) have been studied without recorded death in a follow-up of 18 mo. to 30 yr. This favorable prognosis justifies separation of these pure splenic forms (SCLL) which must be distinguished from what Galton has termed prolymphocytic leukemia (PL). This distinction can be made on the basis of 3 criteria: clinically, SCLL has a slow uneventful course and neither anemia and/or thrombocytopenia; cytologically PL can be distinguished from other forms of CLL though atypical forms of CLL may be confused with the former; and the study of surface membrane immunoglobulins (SmIg) showed that while lymphocytes from most patients with both PL and SCLL bore uniform SmIg, suggesting a monoclonal B[bone marrow derived]-cell proliferation, there was a major quantitative difference. Whereas PL lymphocytes had a number of antigenic sites close to that of normal lymphocytes (mean: 82,000 sites/cell), SCLL lymphocytes had a drastically reduced number of sites. This is an important criterion for the differential diagnosis between PL and SCLL.