The Lymphoproliferative Disease of Granular Lymphocytes: Updated Criteria for Diagnosis

Abstract

Abstract The lymphoproliferative disease of granular lymphocytes (LDGL), also referred to as LGL leukemia, is a heterogeneous disorder, but is clinically, morphologically, and immunologically distinct. Although LDGL has recently been included in the revised classification of lymphomas as an independent clinical entity, no consensus exists on the criteria to establish the diagnosis. The aim of this report was to refine the parameters needed to make the diagnosis of LDGL. We studied 11 patients with chronic granular lymphocytosis selected from among 195 cases observed by our institutions from three different geographic areas (North America, Europe, and Asia). These cases did not meet the current criteria for inclusion in LDGL, since all patients had less than 2,000 GL/μL. However, in each of these patients, we found evidence for expansion of a discrete GL population. Clonal rearrangement of the T-cell receptor (TCR) β gene was found in peripheral blood mononuclear cells (PBMC) of all nine patients with CD3+ LDGL. Using recently generated monoclonal antibodies (MoAbs) against the TCR Vβ gene regions, we identified a unique TCR Vβ on GL from each of three patients studied. In two patients with CD3− LDGL, we also identified a restricted pattern of reactivity, by staining with MoAbs against p58 antigen found on normal natural killer (NK) cells. The clinical features of these 11 patients with relatively low absolute number of GL were similar to those reported previously for patients with greater than 2,000 GL/μL. These data demonstrate that newer techniques such as MoAbs against Vβ gene regions and p58 molecules and molecular analyses are useful to identify expansions of discrete GL proliferations. Demonstration of an expansion of a restricted GL subset is evidence for the diagnosis of LDGL, even in patients with a relatively low GL count. Our results also contribute to distinguish between the end of normality and the beginning of pathology in the broad spectrum of GL lymphocytoses.