[1397] SPI-B a Novel Immunohistochemical Marker for Human Plasmacytoid Dendritic Cell Neoplasms. Characterization of Its Expression in Major Haematolymphoid Neoplasms

S Montes-Moreno, R Ramos, G Roncador, F Acquadro, SM Rodriguez-Pinilla, R Pajares, L Sanchez, MA Piris. CNIO, Madrid, Spain

Background: SPI-B is an Ets family transcription factor that is expressed exclusively in mature B cells, T cell progenitors and plasmacytoid dendritic cells (pDC). SPIB locus has been found to be affected by chromosomal imbalances in ABC type DLBCL. Furthermore SPIB has been shown to be a key regulator of human pDC development and a component of the signature of blastic pDC neoplasms.
Design: The aim of this study was to characterize the protein expression of SPIB in haematolymphoid tissues and neoplasms, including major B and T cell lymphoma types. Also a set of blastic pDC neoplasms and its mimickers have been evaluated. For that purpose we have performed immunohistochemical and western blot analysis using a newly generated monoclonal antibody reactive in FFPE tissues.
Results: SPIB was found to be expressed by two haematolymphoid cell subsets, mature B cells in the pre-plasma cell stage of maturation and plasmacytoid dendritic cells. SPIB protein was identified in the nucleus of the cell with varying intensities according to the cell type and differentiation stage. SPIB protein is expressed with variable intensity among B cell lymphoma types: FL (26+/32), DLBCL (76+/100), MCL (42+/74), CLL/SLL (23+/33), SMZL (12+/38), NMZL&MALT (27+/61) and HL(43+/67). Interestingly SPIB was highly overexpressed in many cases of non-GC type DLBCL (37 intensely pos/55 nonGC vs 21 intensely pos/45 GC type; p<0.05 (chi square)). None of the T cell lymphomas studied showed immunohistochemical expression of SPIB. A series of pDC neoplasms (30 cases), mielomonocytic leukemia (6 cases) and acute myeloid leukemia NOS (2 cases), precursor B (12 cases) & T lymphoblastic leukemia/lymphoma (13 cases), nasal type NK/T cell neoplasms (21 cases) and primary cutaneous T CD4 positive lymphoma of small pleormorphic cells (7 cases) was studied with SPIB moAb. SPIB is highly overexpressed in all pDC tumours, while of the rest, only one case of precursor B lymphoblastic lymphoma showed frank expression of the protein.
Conclusions: SPI B protein is expressed heterogeneously and with variable intensity among B cell lymphoma types. Of interest is the high expression found in nonGC DLBCL cases; its relationship with clinical outcome is being investigated. Furthermore SPIB protein expression can be useful in the diagnosis of blastic plasmacytoid dendritic cell neoplasms because of its high specificity in this particular diagnostic situation.
Category: Hematopathology

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 217, Tuesday Morning

 

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