[1540] Bob1 and Oct2 Expression in Lineage Determination of B-Cell Lymphomas Negative for Conventional B-Cell Markers

Liqun Yin, Jie Xu, Min Li, Vishnu Reddy, Quan Zhou, Huanxin Liu, Peiguo Chu, Qianyun Zhang, Qin Huang, Zifen Gao, Huan-You Wang, Xiayuan Liang, Zenggang Pan. University of Colorado Medical Center, Aurora, CO; UAB, Birmingham, AL; Peking University HSC, Beijing, China; Zagreb University School of Medicine, Jiaxing, Zhejiang, China; Guangzhou Medical College, Guangzhou, Guangdong, China; City of Hope, Duarte, CA; University of New Mexico, Albuquerque, NM; University of California San Diego, La Jolla, CA

Background: Rare cases of B-cell lymphomas do not express conventional B-cell markers (CD20, CD79a, and PAX5), including ALK+ large B-cell lymphoma (ALK+ LBL), plasmablastic lymphoma (PBL), primary effusion lymphoma (PEL), HHV8+ large B-cell lymphoma (HHV8+ LBL), and some cases of high-grade LBL (other LBL). Making an accurate diagnosis of these cases can be challenging, and often requires a large panel of immunohistochemistry (IHC), molecular and cytogenetic studies. B-cell specific transcriptional factors, Bob1 and Oct2, have been shown to be consistently expressed in most, if not all, B-cell lymphomas. Here we investigated the expression of Bob1 and Oct 2 in lineage determination of the B-cell lymphomas aforementioned.
Design: Thirty-three cases were retrieved from our files, including ALK+ LBL (8), PBL (13), PEL (5), HHV8+ LBL (5), and unclassified high-grade LBL (2). The diagnosis for each case was confirmed with necessary studies, including IHC, cytogenetic, FISH and molecular analyses. The IHC results for CD20, CD79a, and PAX5 were reviewed, and additional IHC stains for Bob1 and Oct2 were performed for all cases.
Results: Most of our cases were negative for conventional B-cell markers (CD20, CD79a, and PAX5); only a few cases expressed 1 of these B-cell markers focally and weakly (Table 1). However, Bob1 and Oct2 were positive in 85% (28/33) and 79% (26/33) of cases, respectively, and 94% (31/33) of cases had expression of at least 1 of the 2 markers.
Conclusions: Both Bob1 and Oct2 are very sensitive in confirming the B-cell lineage of B-cell lymphomas otherwise lacking expression of conventional B-cell markers, and the sensitivity is even higher (94%) with combination of these 2 markers.

Table 1
 CD20CD79aPAX5Bob1Oct2Bob1 or Oct2
ALK+ LBL0/80/82/88/86/88/8
HHV8+ LBL0/50/30/43/55/55/5
Other LBL0/20/20/22/22/22/2
Total1/33 (3%)1/30 (3%)5/32 (16%)28/33 (85%)24/33 (73%)31/33 (94%)

Category: Hematopathology

Monday, March 4, 2013 1:00 PM

Poster Session II # 207, Monday Afternoon


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