HER-2/neu amplification, hyperdiploidy, and ERBB2 expression by IHC in breast cancers: A FISH analyses study of 165 cases. T.J. Jodlowski, D.T. Walsh, L.A. Cannizzaro, K.H. Ramesh. Department of Pathology, Montefiore Medical Center, Bronx, NY. 10461.
   Patients with a positive HER-2/neu gene amplification result by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) may undergo further treatment with Herceptin (Trastuzumab) in combination with paclitaxel for a better prognosis. However, limitations in the FISH scoring criteria, including the relationship between hyperdiploidy and amplification, may rule out potential patients from receiving this or other beneficial treatments. By FISH, HER-2/neu amplification status is determined by the number of copies of the HER-2/neu gene localized to 17q11.2-q12, divided by the number of chromosome 17 centromeres present in infiltrating or invasive breast tumor cells. A ratio of 2.2 or greater for HER-2/neu is considered positive for amplification. In our study, cases with a ratio of centromere 17 signals to the number of cells analyzed, greater than 2.5 were considered hyperdiploid. By IHC, 1+ is considered negative for over expression of ERBB2, 2+ is weakly positive, and 3+ is positive. Of the 165 cases that we studied, a significant number were hyperdiploid for centromere 17 and negative for amplification (31%). Although multiple copies of HER-2/neu were indeed present in the hyperdiploid cases in our study, the scoring criteria for amplification dictates these cases to be reported as negative for HER-2/neu amplification. Of our 165 cases, 24% were 2+ by IHC, hyperdiploid and reported as negative for amplification by FISH. Additionally, 4% of our 165 cases were 3+ by IHC, hyperdiploid, and negative for amplification by FISH. Conversely, 5% of our 165 cases that were 3+ by IHC and hyperdiploid were amplified. Based on this study further evaluation of the FISH scoring criteria for HER-2/neu amplification and reporting of hyperdiploidy with or without HER-2/neu gene amplification in breast cancer is strongly suggested. Hyperdiploidy results, with or without HER-2/neu gene amplification obtained from studies on a larger cohort may provide valuable information that could be vital in the treatment and prognoses of patients with aggressive breast tumors.