A germline heterozygous MLH1 gene variant (chr3:g.37053562 C>T; NM_000249.3: c.649 C>T, p.Arg271Cys) was identified from patient 1, who had a history of lung adenocarcinoma and papillary thyroid cancer. The gene discussed is MLH1; the disease is thyroid gland papillary carcinoma.