[1383] MYC Copy Number and Signal Clusters by Colormetric In-Situ Hybridization (CISH) in Diffuse Large B-Cell Lymphoma (DLBCL).

Carlo M Valentino, Nathalie A Johnson, Patrick J Brunhoeber, Hiroaki Nitta, Randy D Gascoyne, Thomas M Grogan, Lisa M Rimsza. University of Arizona School of Medicine, Tucson; British Columbia Cancer Agency, Vancouver, Canada; Ventana Medical Systems Inc., Tucson, AZ; McGill University, Montreal, Canada

Background: Abnormalities of the MYC gene are associated with poor outcome in DLBCL. Increased MYC copy number has been previously reported using fluorescent in-situ hybridization (FISH) and was associated with poor outcome in DLBCL. Dual color CISH is a novel technique that can be used to assess gene copy number. We hypothesized that increased MYC copy number and “clusters” of MYC signals as detected by CISH would be frequent in DLBCL.
Design: Using CISH, we stained 202 cases of DLBCL for both MYC and chromosome 8 centromere (CEN8) (blue and red chromagens, respectively). In each case, we counted the total number of MYC and CEN8 signals in 20 cells. Cases were categorized into three groups based on total MYC and CEN8 copy number. Based on our previous publication, cases with ≤ 44 copies of MYC were considered normal (C. Stasik, Haematologica 2009) and fell into Group 1. Cases with greater than 44 copies of MYC were subdivided into Groups 2 and Group 3 (those with and without increased CEN8 respectively). We also noted the size and shape of the MYC signals. Cases with 4 or more cells having closely packed, enlarged MYC signals were designated as containing “clusters”.
Results: 177/202 cases were successfully stained. 33/177 cases (18.6%) fell into Group 1 (MYC copy number ≤ 44 per 20 cells). MYC copy number was increased in 144/177(81.4%) with an average of 3.3 copies/cell. 85/177 cases (48.0%) fell into Group 2 (MYC copy number >44, CEN8 ≤ 44) and 59/177 cases (33.3%) fell into Group 3 (MYC copy number >44, CEN8 copy number >44). 53/177 cases (29.9%) had “clusters” of MYC signals, the majority (35/53, 66%) of these fell into Group 2, with 3/53 (5.7%) in Group 1, and 15/53 (28.3%) in Group 3.
Conclusions: CISH is a useful technique for evaluation of MYC abnormalities in DLBCL, which may be more frequent than reported. Advantages of CISH include interpretation with a light microscope and a long-lasting signal. MYC copy number was increased most frequently in cases without increased CEN8 signals, indicating low level of MYC amplification rather than polysomy 8. This is the first report of "clusters" of MYC signals in DLBCL and implies that multiple copies of MYC were present which could not be resolved by light microscopy. We plan to correlate our results with presence of MYC translocations, MYC protein by IHC, mRNA, and patient outcome.
Category: Hematopathology

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 184, Monday Morning


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