[1460] Correlation of C-MYC Protein and the Presence of C-MYC Rearrangement in High Grade B-Cell Lymphoma

Zhicheng Mo, Calvin Chen, Serhan Alkan, Randa Alsabeh. Cedars-Sinai Medical Center, Los Angeles, CA

Background: The presence of C-Myc gene rearrangements is not only important for the diagnostic workup of aggressive B cell lymphoma, but also entails poor response to R-CHOP based chemotherapy and worse prognosis in diffuse large B-cell lymphoma(DLBCL). The standard detection for C-Myc aberrations is fluorescence in situ hybridization (FISH) and karyotyping. However, these techniques are expensive and not widely available. The aim of this study is to evaluate C-Myc immunohistochemistry and its correlation with C-Myc rearrangement by FISH.
Design: High-grade B cell lymphomas diagnosed between 2010 and 2012 in which C-Myc status was investigated as part of the diagnostic work-up were selected. Immunohistochemistry (IHC) was performed with automated immunostainer using rabbit monoclonal antibody against C-Myc protein from two different manufacturers, Ventana and Epitomic respectively. C-Myc protein expression by IHC was evaluated based on percentage of positive cells and recorded in qualitative fashion.
Results: A total of 42 cases were selected: 33 DLBCL, four Burkitt lymphomas and five B cell lymphoma with features intermediate between DLBCL and Burkitt lymphoma. Overall, the results were similar using the antibodies from the two different vendors. There were 13 cases that demonstrated C-Myc gene rearrangement by FISH. By IHC, 11 out of 13 cases had significantly stained positive cells (a mean of 85.9% : range: 75% to 95%) while 2 out of 13 showed very low positivity (5-10%). Lymphomas lacking C-Myc gene translocation by FISH (29 cases), had very low number of positive cells in majority of cases (28/29) 15.3% (range: 0-50%) while only one case (1/29) was strongly positive (90%) for C-Myc by IHC.
Conclusions: There is significant correlation in between strong staining of C-Myc protein (>70%) and presence of C-Myc gene translocation by FISH. However, weak expression of C-Myc protein can be observed in 15% of cases with C-Myc translocation while C-Myc positivity, although rare,can be observed in 3% cases lacking C-Myc translocation. Although, C-Myc immunohistochemistry can be a useful screening test, FISH should remain as the standard test for detecting C-Myc gene rearrangement.
Category: Hematopathology

Monday, March 4, 2013 1:00 PM

Poster Session II # 205, Monday Afternoon

 

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