[MUTYH-associated polyposis: Review and update of the French recommendations established in 2012 under the auspices of the National Cancer Institute (INCa)]

[Prophylactic gastrectomy]

One to 3% of gastric cancers are secondary to genetic predisposition, notably hereditary diffuse gastric cancers (HDGC) caused by CDH1 gene mutations. According to French recommendations, in case of CDH1 gene mutation, a prophylactic total gastrectomy should be performed between 20 and 30 years old. This gastrectomy should remove all the gastric mucosa at both extremities (duodenal and esophageal sides). Histopathological examinations of prophylactic total gastrectomies in asymptomatic CDH1-mutated patients reveal microscopic foci of diffuse-type cancer in 90 to 100% of cases. Lymph node involvement and lympho-vascular invasion are extremely rare, justifying the use of a D1-only lymphadenectomy. In the context of prophylaxis, limited lymphadenectomy and the development of minimally invasive oesogastric surgery, the minimally invasive approach might be the preferred approach, in expert centers. Surgical outcomes seem to be similar to those after gastrectomy for cancer. Prophylactic total gastrectomy is the cornerstone of CGDH management, associated with multidisciplinary follow-up and mammary surveillance in women.

Case Series of 11 CDH1 Families (47 Carriers) Including Incidental Findings, Signet Ring Cell Colon Cancer and Review of the Literature

Germline pathogenic variants in E-cadherin (CDH1) confer high risk of developing lobular breast cancer and diffuse gastric cancer (DGC). The cumulative risk of DGC in CDH1 carriers has been recently reassessed (from 40-83% by age 80 to 25-42%) and varies according to the presence and number of gastric cancers in the family. As there is no accurate estimate of the risk of gastric cancer in families without DGC, the International Gastric Cancer Linkage Consortium recommendation is not straightforward: prophylactic gastrectomy or endoscopic surveillance should be proposed for these families. The inclusion of CDH1 in constitutional gene panels for hereditary breast and ovarian cancer and for gastrointestinal cancers, recommended by the French Genetic and Cancer Consortium in 2018 and 2020, leads to the identification of families with lobular cancer without DGC but also to incidental findings of pathogenic variants. Management of CDH1 carriers in case of incidental findings is complex and causes dilemmas for both patients and providers. We report eleven families (47 CDH1 carriers) from our oncogenetic department specialized in breast and ovarian cancer, including four incidental findings. We confirmed that six families did not have diffuse gastric cancer in their medical records. We discuss the management of the risk of diffuse gastric cancer in Hereditary Lobular Breast Cancer (HLBC) through a family of 11 CDH1 carriers where foci were identified in endoscopic surveillance. We also report a new colon signet ring cancer case in a CDH1 carrier, a rare aggressive cancer included in CDH1-related malignancies.