- Clinical (e.g. a constitutional mismatch repair deficiency score ≥ 3; Wimmer et al. 2014) and/or other hints (e.g. absent intratumoral immunohistochemical expression of at least one of the MLH1, MSH2, MSH6, or PMS2 mismatch repair proteins and/or high microsatellite instability) for an underlying biallelic (constitutional) mismatch repair deficiency (bMMRD/CMMRD) or a heterozygous mismatch repair deficiency (hereditary non-polyposis colon cancer syndrome/HNPCC syndrome/Lynch syndrome): These patients and their relatives should be offered human genetic counseling and rapid genetic diagnostics to confirm or rule out these conditions. These patients might not benefit from the present study treatment but maybe from other therapeutic strategies (Bouffet et al. 2016). Since patients with clinically suspected neurofibromatosis type 1 may display similar symptoms as in CMMRD, patients with clinically suspected neurofibromatosis type