BRCA2-Related Hereditary Cancer Syndrome-Associated Small Bowel Adenocarcinoma With Multiple BRCA2 Mutations: A Case Report and Review of the Literature

Background: Small bowel adenocarcinomas (SBAs) are rare and aggressive cancers. About one-fifth of SBA patients have predisposing conditions; among them, there are also genetic tumor syndromes, including Lynch syndrome, familial adenomatous polyposis, and Peutz-Jeghers syndrome. Although BRCA2 mutations, both somatic and germline, have been recently described in SBAs, direct evidence of BRCA2 inactivation in SBA tumor tissue of patients with BRCA2-related hereditary cancer syndrome is still very limited. Case Presentation: Herein, we described a case of a 51-year-old woman with a history of breast cancer who developed an adenocarcinoma of the duodeno-jejunal flexure causing persistent vomiting. After clinical staging, the patient underwent surgical resection, and histologic examination of the specimen confirmed a poorly differentiated adenocarcinoma infiltrating the visceral peritoneum and showing lymph node metastases (stage III, pT4N1). Two years later, the SBA relapsed, and next generation sequencing was performed in matched tumor and normal tissues. In addition to KRAS and TP53 mutations in the tumor, both somatic and germline BRCA2 mutations were identified, indicating biallelic BRCA2 alterations. Conclusion: BRCA2-associated hereditary tumor syndrome could have an etio-pathogenetic role in SBA development; thus, we suggest that this syndrome should be considered in patients with an SBA diagnosis below the age of 50 years, especially when a personal or family history of breast cancer is present.