Verification of Rabbit Monoclonal Antibody Progesterone Receptor Clone YR85 in Invasive Breast Cancers Using Clone PgR636
Haiping Liu, Sharmini Muralitharan. Thermo Fisher Scientific, Anatomical Pathology Division, Fremont
Background: Clone YR85, a relatively new rabbit monoclonal anti-progesterone receptor antibody, demonstrated potential clinical usefulness by presenting distinct nuclear staining in a set of known PR positive breast cancer samples. To further characterize the antibody, a comparison study has been carried out between this clone and the well established clone PgR636.
Design: Three breast cancer tissue microarrays consisting of a total of 210 cases were used to evaluate the concordance of the rabbit monoclonal antibody clone YR85 and clone PgR636. Two normal tissue microarrays and one multi-tumor microarray were stained with both clones to survey the distribution in non-breast cancer cases and to investigate possible non-specific staining. A mini PR microarray served as the control. Normal breast tissue cores and benign breast lesions were also present in some of the microarrays serving as general control. All tissues were fixed within 30 minutes of removal in 10% NBF for 24 hrs. The IHC of the two clones was performed in parallel in an Autostainer and stained using UltraVision Quanto HRP detection system. The percentage of invasive tumor cells exhibiting nuclear staining and staining intensity was reported. A cutoff of a minimum of 1% of tumor cells positive for PR in samples was considered positive.
Results: A total of 197 invasive breast cancer cases were valid for data analysis. There was a good representation of cases with various expression levels in the cohort. The overall concordance between clone YR85 and the reference clone PgR636 was 92.9%; the concordance for PR positive category was 92.7% and for PR negative category was 93.0%. The Cohen's Kappa Coefficient was 0.854.
In the distribution survey, the two PR clones were stained on two normal tissue microarrays and a multi tumor microarray consisting of 35 normal tissue types and 40 tumors types covering most of the common benign, malignant and metastatic tumors. As expected, clone YR85 nuclear staining was also observed in the cells of other reproductive organs other than breast. Clone YR85 staining was not found in most non-reproductive organs, except one of the five normal pancreatic tissues tested. This is consistent with the performance of the clone PgR636 which also stained positive in the same pancreatic tissue core with the same staining pattern.
Conclusions: This verification study confirms that clone YR85 performs with high concordance to the reference clone PgR636 in detecting progesterone receptor in invasive breast cancers and other reproductive organs.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 33, Wednesday Afternoon