1. ¹Department of Clinical and Experimental Medicine, University of Verona, Verona, Italy
2. ²Department of Pathology, University of Verona, Verona, Italy
3. ³Department of Oncology, Università Vita-Salute San Raffaele and Istituto Scientifico San Raffaele, Milano, Italy
4. ⁴Department of Medicine and Public Health, University of Verona, Verona, Italy
5. ⁵Institute for Cancer Research and Treatment, IRCC, Candiolo e Ospedale Mauriziano 'Umberto I', Torino, Italy

Correspondence: Professor A Ambrosetti, Dipartimento di Medicina Clinica e Sperimentale, Sezione di Ematologia, Università di Verona, Policlinico G.B. Rossi., Piazzale L.A. Scuro 10, 37134 Verona, Italy. E-mail: achille.ambrosetti@univr.it

Received 20 April 2006; Revised 19 September 2006; Accepted 26 September 2006; Published online 2 November 2006.

Abstract

Zeta-associated protein-70 (ZAP-70), mostly assessed by flow-cytometry (FC), recently emerged as reliable prognostic factor in chronic lymphocytic leukaemia (CLL) at presentation. We evaluated ZAP-70 expression in 156 CLL patients by immunohistochemistry (IHC) on formalin-fixed bone marrow (BM) biopsies at diagnosis. At presentation, 117 patients (75%) were with Binet stage A, 27 (17%) stage B and 12 (8%) stage C. Median follow-up was 61 months (range 6–242). ZAP-70 was expressed in neoplastic lymphocytes of 69 patients (44%). Concordance between ZAP-70 by IHC and ZAP-70 by FC, immunoglobulin heavy chain variable genes (IGHV) mutational status and CD38 expression was found in 41/46 (89%), 41/49 (80%) and in 60/88 (68%) tested cases, respectively. ZAP-70 expression significantly correlated with advanced Binet stage (B–C), diffuse BM infiltration, increased lactate dehydrogenase (LDH) and 2-microglobulin serum levels and lymphocyte doubling time <12 months. ZAP-70 positivity was significantly related to poorer time to progression (median 16 months vs 158 of ZAP-70-negative cases) (P<0.0001) and overall survival (median 106 months vs not reached) (P=0.0002); this correlation was confirmed at multivariate analysis. ZAP-70 expression correlated with poorer outcome also when evaluated only in the 117 stage A patients. In conclusion, immunohistological detection of ZAP-70 on formalin-fixed BM biopsies at diagnosis appears a useful methodological approach to identify patients with poor prognosis in CLL.