[Metachronous colon cancer after successful treatment of mismatch repair-deficient metastatic colorectal cancer].

Colorectal cancer (CRC) is considered to be a heterogeneous disease with different molecular subtypes based on the expression status of mismatch repair (MMR) e.g. It is well known that tumours with mismatch repair deficiency (dMMR) are associated with better prognosis, as well as a more effective response to immunotherapy. In this case report, a patient is diagnosed with three new dMMR tumors in the colon 3,5 years after successful treatment with immunotherapy for metastatic CRC. Until now, retreatment with immunotherapy has not been described in the literature, and this case report describes the advantages and disadvantages from this perspective.