A Multi-institutional Study of Interlaboratory Variance in the Estrogen and Progesterone Receptor Assays

Purpose The expression of hormone receptors is the most reliable factor for predicting the responsiveness to hormonal therapy At present, immunohistochemistry (IHC) is considered as a practically reliable method. This study was designed to examine the interlaboratory variance in immunohistochemical assays for estrogen receptor (ER) and progesterone receptor (PR) in Korea Methods The Korean Study Group for Breast Pathology (KSGBP) made a questionnaire to know the current situation in HR assay in Korea. The questionnaire was sent to the members of KSGBP by e-mail, which were included eight questions relating to tissue handling, ER/PR IHC procedure and interpretation method. Forty laboratories replied with the completed questionnaire Results All 40 laboratories were using formalin as a fixative. Pretreatment was performed using six different methods including autoclave (25%), microwave (30%) and full autostainer (15%). Primary antibodies for ER were SP1 in 40%, 6F11 in 27.5% and 1D5 in 32.5%. Primary antibodies for PR were more variable (seven clones) than those for ER Interpretation method used was Allred system in 20%, modified Allred system in 15%, report the % of positive tumor cells in 45%, positive/negative in 15% and others in 5% The expression rate of ER was ranged from 45.6% to 93% (mean 635%) and the expression rate of PR was ranged from 27% to 90% (mean 59 1%) The differences according to the numbers of breast cancer in each institute, primary antibodies, detection systems and interpretation methods did not influence to the expression rate of ER/PR, statistically (p>0 05) Conclusion In Korea, the interlaboratory variance in ER/PR IHC procedure was too huge to make a standardized method We suggest the proper quality control program such as ER/PR staining with positive internal and external controls and negative control might be better to aim at getting similar results among the different laboratones rather than trying to standardize the procedure