LYMPHOCYTIC LEUKEMIA. A STUDY OF 335 UNTREATED CASES FROM A SINGLE INSTITUTION

urrent staging systems for chronic lym-phocytic leukemia (CLL) that include a certain number of clinical variables have been widely accepted as defining life expectancy and optimal therapeutic management of the disease.1-3 The prognostic importance of stage has recently been confirmed in a large series of patients by the MRC CLL trial,4 as well as by many others in the past. Nevertheless, it is still unclear why within the low risk stages some patients develop unpre-dictably more aggressive disease while others show an indolent course. This observation lead to investigation of the prognostic value of other clinical factors not included in the well-known staging criteria. In the last decade, the histologic bone mar-row (BM) pattern of infiltration in CLL and its prognostic significance have been the subject of several studies, and it is generally agreed that patients with a diffuse pattern of BM infiltra-tion are characterized by advanced stage and poor prognosis.5-12 Recently, the Spanish Cooperative Group for CLL demonstrated that the BM histologic pat-tern has emerged as the best independent prog-nostic parameter;13 moreover, Pangalis et al