PTEN and breast carcinoma: Similarly, PTEN changes were reported in the MK-2206 monotherapy trial in metastatic/advanced breast cancer patients, where PTEN expression by IHC was assessed in both archival samples and samples procured just prior to MK-2206 treatment in 22 patients.11 In all, 19 (86%) had concordant results, 2 had PTEN loss in the archival samples and no PTEN loss in the recent samples, and 1 had PTEN loss in the recent sample and no PTEN loss in the archival sample.