Fraune C, Simon R, Höflmayer D, et al. - A total of 316 advanced prostate cancers were examined by researchers via immunohistochemistry (IHC) for the mismatch repair (MMR) proteins MLH1, PMS2, MSH2, and MSH6 on a TMA format to identify prostate cancers with microsatellite instability (MSI). Of 200 interpretable cancers, IHC findings were uniform with MSI in 10 tumors. For the MMR status, the absence of intratumoral heterogeneity indicated that MSI occurs early in prostate cancer. Thus, researchers concluded that, on limited biopsy material by IHC, MMR analysis is satisfactory to evaluate the MMR status of the whole cancer mass.