PGR and cancer: However, although we cannot entirely exclude this possibility, previous studies by others have shown that with use of the standard breast cancer prognostic markers (ER, PR and HER-2), two cores are sufficient and have resulted in >95% accuracy.40–42 Similarly, two cores have also been reported to provide a high level of accuracy in the TMA analysis of other cancers, such as metastatic prostate and ovarian cancer.43,44