2005 Articles

CD117 expression in diffuse large B-cell lymphomas: Fact or fiction?

Vakiani, Efsevia; Cattoretti, Giorgio; Colovai, Adriana I.; Vundavalli, Murty V.; Alobeid, Bachir; Bhagat, Govind

CD117 (KIT) is expressed in a variety of hematopoietic neo- plasms but there are a paucity of data regarding its expres- sion in diffuse large B-cell lymphomas (DLBCL). The purpose of the present paper was to describe the authors’ experience of two CD117+ DLBCL (one of follicle center-cell origin and one nasal Epstein–Barr virus (EBV)– plasmablas- tic lymphoma associated with lytic bone lesions), as deter- mined by tissue immunohistochemistry and flow cytometry. The CD117 expression in DLBCL was further evaluated using tissue microarrays and seven additional plasma- blastic lymphomas, using two commercially available anti-CD117 antibodies (Ab-1, Oncogene and A4502, Dako- Cytomation). Membranous ± cytoplasmic staining was seen with Ab-1 in 24/65 (37%) DLBCL, including 21/56 microarray DLBCL, two index cases, and 1/7 additional plasmablastic lymphomas, with persistent staining in 13% of microarray DLBCL despite preincubation with KIT peptide. However, A4502 had only membranous staining of the index cases and one additional EBV– plasmablastic lymphoma with medullary disease. The present study suggests that (i) CD117 expression can be detected sporadically in DLBCL of follicle center-cell origin and a subset of plasmablastic lymphomas; (ii) staining for CD117 might help in identifying EBV– plasmablastic lymphomas associated with bone mar- row involvement; and (iii) CD117 antibodies should be care- fully validated prior to use, because non-specific staining, as observed with Ab-1, could lead to false-positive results.