Does Estrogen Receptor Expression Vary with Fixation Time?
JA Ibarra, LW Rogers. MemorialCare Breast Center at OCMMC, Fountain Valley, CA; MemorialCare Breast Center at LBMMC, Long Beach, CA
Background: ER expression by IHC is said to vary with the time of fixation. However, only limited published data exist addressing this subject (Goldstein). In contrast to usual pathology practice, the tissue in that study was not processed immediately after formalin fixation. Instead the blocks were maintained in 100% cold ethanol prior to transfer to the tissue processor where there was an additional 90 minutes fixation in heated (40C) 20% formalin prior to the dehydration steps.
Design: The goal of this pilot study is to examine 10 cases. Small pieces (4x4x2mm) 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 1 hr, 3 hrs, 6 hrs and 9-10 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 using a fast routine protocol for 2:30 hrs in a Shandon Excelsior tissue processor that did not include additional time in formalin. All blocks were then batch stained with rabbit antibody SP1 clone for estrogen receptor using the Ventana Benchmark XT automated processor. All cases were invasive carcinomas known to be estrogen receptor positive before inclusion in the study. Two pathologists reviewed every slide independently and the stains were evaluated as follows: Intensity of nuclear staining (1+, 2+, or 3+) and percentage of positive tumor cells.
Results: Five cases of invasive breast carcinoma have been analyzed thus far. All blocks, regardless of whether they were fixed for 1, 3, 6, or 9-10 hrs had strong and diffuse nuclear staining with ER. No significant staining difference was noted between the various fixation times.
Conclusions: Fixation times in 10% buffered formalin between 1 and 9 hrs do not affect ER expression. Further studies are needed to confirm this finding. Reference: Goldstein NS. Recommendations for improved standardization of immunohistochemistry. Appl Immunohistochem Mol Morphol 2007;15:124-133
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 3, Wednesday Morning