{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,30]],"date-time":"2026-03-30T13:41:21Z","timestamp":1774878081422,"version":"3.50.1"},"reference-count":16,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2022,11,28]],"date-time":"2022-11-28T00:00:00Z","timestamp":1669593600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>Lynch syndrome (LS) is a genetic disorder mainly caused by germline mutations in mismatched repair (MMR) genes (<jats:italic>MSH2<\/jats:italic>, <jats:italic>MLH1<\/jats:italic>, <jats:italic>MSH6<\/jats:italic>, and <jats:italic>PMS2<\/jats:italic>) or deletions of the epithelial cell adhesion molecule gene (<jats:italic>EPCAM<\/jats:italic>). A 43-year-old Chinese male patient underwent radical surgery and was pathologically confirmed to have stage IIIB colon adenocarcinoma. After four cycles of standard adjuvant chemotherapy, the tumor reoccurred <jats:italic>in situ<\/jats:italic> with intestinal obstruction. The patient received secondary colectomy. Immunohistochemistry analysis revealed a loss of MSH2 protein expression in the surgical specimen. Noticing that the patient\u2019s mother and grandfather all were diagnosed with LS-related cancers, we collected the patient\u2019s and his mother\u2019s peripheral blood for genetic testing, and the result showed a six-base deletion of <jats:italic>MSH2<\/jats:italic>. Thus, we concluded that our patient had LS. Subsequently, the patient accepted pembrolizumab as the first-line systemic therapy after liver metastases. He achieved clinical complete response (cCR) within 2 months and remained progression-free for more than 2 years. The case report showed that <jats:italic>MSH2<\/jats:italic> mutation (c.489_494deTGGGTA) is a likely pathogenic mutation, and immunotherapy (pembrolizumab) is effective for this patient.<\/jats:p>","DOI":"10.3389\/fimmu.2022.1064488","type":"journal-article","created":{"date-parts":[[2022,11,28]],"date-time":"2022-11-28T06:58:50Z","timestamp":1669618730000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":4,"title":["Case report: Complete response to pembrolizumab in a liver metastatic colon adenocarcinoma patient with a novel likely pathogenic germline MSH2 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