ZAP70 May be 'Easily Determined' in Marrow Biopsy Specimens

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ublished Online First: 17 August 2006. doi:10.1136/jcp.2006.039586

Journal of Clinical Pathology 2007;60:627-632

© 2007 by BMJ Publishing Group Ltd & Association of Clinical Pathologists

ORIGINAL ARTICLE

B cell chronic lymphocytic leukaemia/small lymphocytic lymphoma: role

of ZAP70 determination on bone marrow biopsy specimens

Elena Sabattini1, Rocio Orduz1, Cristina Campidelli1, Pier Luigi

Zinzani2, Vincenzo Callea3, Simona Zupo4, Giovanna Cutrona4, Fortunato

Morabito5, Manlio Ferrarini4 and Stefano Pileri1

1 Haemolymphopathology Service, St Orsola Hospital, University of

Bologna, Bologna, Italy

2 Institute of Haematology, St Orsola Hospital, University of Bologna,

Bologna, Italy

3 Service of Haematology, Bianchi Melacrino Morelli Hospital, Reggio

Calabria, Italy

4 Division of Medical Oncology, Institute of National Cancer Research,

University of Genova, Genova, Italy

5 Service of Haematology, Dell'Annunziata Hospital, Cosenza, Italy

Background: The course of chronic lymphocytic leukaemia/small

lymphocytic lymphoma (CLL/SLL) partly depends on the mutational status

of the variable region of immunoglobulin heavy chain genes (IgVH),

which defines two subgroups of tumours: mutated and unmutated. The

expression of zeta-associated protein 70 (ZAP70) is significantly

associated with the more aggressive unmutated forms.

Aims: To assess the feasibility of the ZAP70 immunohistochemical test

on bone-marrow biopsy (BMB) specimens and to compare the results with

those of western blotting (WB) and IgVH mutational status assessed on

neoplastic cells from peripheral blood.

Methods: 26 patients with CLL/SLL detected on BMB and with known IgVH

mutational status were selected. ZAP70 was determined by

immunohistochemistry (IHC) comparing three antibodies from different

sources (Upstate, Cell Signaling, Santa Cruz, California, USA) and two

different methods (APAAP and EnVision+). In 23 cases, ZAP70 WB results

were also available.

Results: ZAP70 determination on BMB specimens turned out to be easily

feasible with routine procedures with reagents from Upstate and Cell

Signaling. The results were concordant with those obtained with WB and

mutational status analysis in >80% of the cases with both reagents.

Three of four discordant cases were mutated/ZAP70 positive, with two

staining weakly for ZAP70 on both WB and IHC.

Conclusions: The study confirms the role of ZAP70 as a possible

surrogate of mutational status and emphasises its application in

routine diagnostics; it discloses a small subset of discordant cases

(mutated/ZAP70 weakly positive) that clinically cluster with the more

favourable forms.