[1435] Investigation of the Co-Expression of Bob-1 and Oct-2 in Classical Hodgkin Lymphoma Using an Immunohistochemical Double Staining Method

BS Shackley, H Rashidi, ST Pullarkat, J Truell, B Castor, JW Said. University of California Los Angeles, Los Angeles, CA; University of California San Diego, San Diego, CA

Background: The neoplastic Hodgkin/Reed Sternberg (HRS) cells of classical Hodgkin lymphoma (CHL) are known to be of B-cell origin in the majority of cases; however they consistently lack immunoglobulin (Ig) expression. Although the etiology of impaired Ig production in HRS has not been fully explained, recent studies have focused on deficiencies in transcription factors required for Ig gene expression. In particular, octamer-binding transcription factor 2 (Oct-2), and B-cell Oct-binding protein 1 (Bob-1) are critical for proper binding and activation of the Ig promoter. It is generally accepted that HRS cells do not co-express Bob-1 and Oct-2. Indeed, the lack of expression of either of these transcription factors is used as a diagnostic tool favoring CHL in many practices. It has been our experience, however, that a significant number of CHL cases show expression of both Bob-1 and Oct-2. To our knowledge, no study utilizing a double immunostain for Bob-1 and Oct-2 has been reported in the literature.
Design: Forty-two cases of CHL, eight cases of diffuse large B-cell lymphoma (DLBCL), and a single case of anaplastic large cell lymphoma (ALCL) were stained using both Bob-1 and Oct-2 antibodies. The double stained sections were then evaluated and the intensity and percentage of positive cells was documented. Each case was categorized as positive for Bob-1, positive for Oct-2, double positive, or double negative based on the expression pattern of the majority of the neoplastic cells. The intensity of each stain was evaluated on a scale of 1-3.
Results: As expected, 100% of the DLBCLs were double positive for Bob-1 and Oct-2 and the ALCL was double negative. Of the forty-two cases of CHL, 14% demonstrated Oct-2 expression only, 7% demonstrated Bob-1 expression only, 10% demonstrated dual staining, and 69% were double negative. The staining intensity in the eight cases of DLBCL was uniformly strong (3+) while the HRS cells exhibited variable staining intensity.
Conclusions: The double staining method used in this study proves that HRS cells can co-express Bob-1 and Oct-2 and implies that their use as a diagnostic tool for CHL may be limited. This finding also has implications for the mechanism of Ig deficiency in HRS cells and suggests that factors other than Bob-1 and Oct-2 may be involved in Ig transcription.
Category: Hematopathology

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 190, Monday Morning


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