Does Her2neu Expression Vary with Fixation Time?
JA Ibarra, LW Rogers. Memorial Care Breast Center at Orange Coast, Fountain Valley, CA; MemorialCare Breast Center at Long Beach, Long Beach, CA
Background: It is said that Her2neu expression by IHC varies with the time of fixation in neutral buffered formalin. However, there are no published data validating this claim. The published guidelines(1) from ASCO and CAP recommend that the tissue fixation window should be between 6 and 48 hrs in order to reliably perform IHC for Her2neu. In many pathology practices this guideline can present logistic problems, particularly with cases received on Thursday and Friday.
Design: The goal of this pilot study is to examine 10 cases. Punch biopsy samples (3 mm) from tumors removed as part of patient's treatment were obtained immediately after receipt of the lumpectomy or mastectomy in the laboratory. These samples were immediately placed in 10% buffered formalin for 3 hrs, 48 hrs, 72 hrs, 96 hrs and 120 hrs. The tumors were large enough that the small samples removed did not compromise the analysis of the case. The study samples were not stained until the case was completed. After the fixation periods, each block was immediately processed. All cases, except for 5,7 and 10 were processed for 2:45 hrs in a Shandon Excelsior tissue processor. Case 5-48 hrs and case 10-3hrs were processed for 4 hrs in a Leica Peloris tissue processor. The remainder of cases 5, 7, and 10 were processed overnight for 11 hrs. All blocks were then batch stained with PATHWAY Her2neu Clone 4B5 rabbit monoclonal using Ventana Ultraview DAB detection kit in a Ventana Benchmark™ XT processor. All cases were invasive carcinomas known to be Her2neu overexpressers before inclusion in the study. Two pathologists reviewed every slide independently following the ASCO/CAP guidelines (1).
Results: Eight cases of invasive breast carcinoma have been analyzed thus far. All blocks, regardless of whether they were fixed for 3, 48, 72, 96, or 120 hrs had strong and diffuse membranous staining with Her2neu. No significant staining difference was noted between the various fixation times.
Conclusions: Fixation times in 10% buffered formalin between 3 and 120 hrs do not affect Her2neu expression. Further studies are needed to confirm this finding. Reference: American Society of Clinical Oncology/College of American Pathologists guideline recommendations for human epidermal growth factor receptor 2 testing in breast cancer. Arch Pathol Lab Med 2007;131:18-43.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 17, Tuesday Afternoon