最近，双等位基因MSH3的胚系致病/可能致病变异被认为是腺瘤性息肉的一种罕见原因。我们报道了一位49岁的女性，她由于在进行乳腺和卵巢癌遗传相关基因的胚系（可能）致病变异检测时偶然发现了一种双等位MSH3（可能）致病变异而被转诊到我们的高风险结直肠癌门诊。本案例报告的重点是描述我们的患者MSH3相关腺瘤性息肉的基因型和表型。超过一半的息肉（13/19）位于右结肠。此外，良性和恶性的肠外病变可能很常见，因为我们的患者有简单的肝囊肿、肾囊肿和两个基底细胞皮肤癌。版权所有 © 2023. Publicado por Elsevier España, S.L.U.

Recently, biallelic MSH3 germline pathogenic/likely pathogenic variants have been recognised as a rare cause of adenomatous polyposis. We present a 49-year-old woman who was admitted to our high-risk colorectal cancer clinic after incidental detection of a biallelic MSH3 (likely) pathogenic variant when tested for the germline (likely) pathogenic variants in hereditary breast and ovarian cancer related genes. The focus of this case report is to describe the genotype and phenotype of our patient with MSH3-related adenomatous polyposis. More than half of the polyps (13/19) were located in the right colon. In addition, benign and malignant extraintestinal lesions may be common as our patient had simple liver and kidney cysts and two basal cell skin carcinomas.Copyright © 2023. Publicado por Elsevier España, S.L.U.