Strong BOB1 and OCT2 Expression Is Useful for Confirming B-Cell Lineage in PEL and Other Neoplasms with Plasmacytic/Plasmablastic Differentiation
Calvin K Chen, ZhiCheng Mo, Elizabeth Moschiao, Michael Schmidt, Serhan Alkan. Cedars-Sinai Medical Center, Los Angeles, CA
Background: Primary effusion lymphoma (PEL) is a neoplasm presenting as serous effusion without involving any solid organ, typically associated with HHV8 while occasional solid counterpart also occurs as extracavitary PEL. Typically PEL shows immunoblastic or plasmablastic features, expressing CD30, CD138, and MUM1 while the lineage specific markers are usually negative, such as CD3, CD20, and PAX5. Since lineage specific markers are lacking, gene rearrangement is used for linage analysis that may delay the diagnosis. Recently recognized transcription factors, BOB1 and OCT2, have been shown to be necessary for B cell proliferation and immunoglobulin gene expression. We wish to analyze the presence of these transcription factors as an aid for demonstration of B cell lineage in PEL and other plasmacytic/plasmablastic neoplasms.
Design: Whole tissue sections from 35 neoplasms were evaluated: 11 PEL, 5 diffuse large B cell lymphoma (DLBCL), 11 plasmablastic lymphoma (PBL) and 11 plasmacytoma. All selected cases were assessed by large panel of antibodies, including lineage specific markers such as CD20, CD3, CD5, CD79a, CD45, MUM1, PAX5, and CD138 and genotypic analysis. Immunohistochemistry was performed using polyclonal antibodies against BOB1 and OCT2 proteins on all 36 neoplasms. Staining intensity (0-3+), nuclear and cytoplasmic staining patterns were scored. Staining present in greater than 30% of tumor cells was considered positive.
Results: All 11 cases of PEL showed nuclear expression of BOB1 and OCT2 with variable cytoplasmic staining. Staining intensity in PEL was 3+ in 9/11 cases. Furthermore, the PBL and plasmacytoma cases all stained similar to PEL with strong 3+ nuclear staining intensity in 10/11 and 10/11 cases, respectively. All cases of DLBCLs showed strong 3+ nuclear and cytoplasmic staining for BOB1 and OCT2 expression.
Conclusions: BOB1 and OCT2 transcription factors are concurrently expressed by B cell neoplasms including PEL, PBL, DLBCL, and plasmacytoma. Although T-cell neoplasms to a lower extent is reported to express BOB1 and OCT2, strong expression has never been observed including peripheral T-cell lymphomas. Therefore, integrated analysis of BOB1 and OCT2 together with absence of T-cell lineage specific markers could be used as a strong surrogate evidence of B-cell lineage in neoplasms with suspicion of PEL or plasmablastic/plasmacytic neoplasms.
Monday, March 4, 2013 1:00 PM
Poster Session II # 208, Monday Afternoon