MRC1 and mismatch repair cancer syndrome 1: A total of 542 of 597 (91%) cancers on the TMA were considered interpretable for MMR status, because either an unequivocal loss of staining of at least one of the four examined MMR proteins MLH1, PMS2, MSH2, or MSH6 was seen (MMR deficiency) or unequivocally retained expression of at least 3 MMR proteins without concomitant loss was observed (intact MMR status).