Hormone Receptor Immunohistochemistry: The Prevalence of ER-PR+ Results Are PR Antibody Clone-Dependent
DC Gingell, R Bhargava, DJ Dabbs. Magee-Women's Hospital of UPMC, Pittsburgh, PA
Background: One of the single-positive categories of hormone receptors (HR) by IHC is the ER-/PR+ group. This category was documented with the ligand-binding method of HR assay and comprises a small fraction cases by immunohistochemistry (IHC). Some argue that poor tissue fixation yielding a false-negative ER is the reason for these results. We have previously demonstrated that fixation is not related to the negative ER result (Mod Pathol. 2008;21(supp 1):27A-abstract 111). To further characterize the nature of the ER-/PR+ category, we compared two ER clones and three PR clones to ascertain whether the prevalence of the ER-/PR+ category is clone driven.
Design: One hundred and ten ER-/PR+ cases from a 30 month period, Jan 1, 2005-June 30, 2007 were available for study, comprising 5.7% of the total cases for this time period. Criterion for a positive result for ER or PR was any nuclear expression. These results utilized ER 6F11 and PR 1A6 clones on the Benchmark XT according to FDA kit protocols. The same cases were studied with ER clone SP1 and PR clone 1E2 on the Benchmark XT with FDA kit protocols. In addition PR clone 636 on the Dako autostainer with FDA protocol was also performed. Results were tabulated according to any nuclear expression and >1% of cells with nuclear expression.
|Any + Nuclei (No. of cases/%)||>1% + Nuclei (No. of cases/%)|
Conclusions: (1) ER-/PR+ cases are seen by the IHC method even with optimal fixation methods. (2) The number of ER-/PR+ cases is highly dependent upon the clone of PR used, with clone 1A6 yielding the highest percentage, more than four-fold compared to the 1E2 and 636 PR clones. (3) The method of determining a positive result -any cells positive vs >1% of cells positive also has an impact on ER-PR+ metrics. (4) SP1 ER clone yields 8% more positive cases compared to ER 6F11, a result comparable to data previously published (Cheang MC et al J Clin Oncol 2006;36:5637-44 ).
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 4, Wednesday Morning