Familial Gastrointestinal Stromal Tumor with Germline KIT Mutations Accompanying Hereditary Breast and Ovarian Cancer Syndrome

BACKGROUND: Familial gastrointestinal stromal tumor (GIST) is a rare disease with germline mutations in the c-kit gene (KIT) or platelet-derived growth factor receptor alpha gene (PDGFRA). We had encountered multiple GISTs in the stomach and small intestine during a screening of ovarian cancer for a woman with hereditary breast and ovarian cancer syndrome (HBOC) with breast cancer susceptibility gene II (BRCA2) mutations. The aim of this study was to examine this case in detail. CASE REPORT: A 65-year-old woman diagnosed with HBOC harboring BRCA2 mutations was found to have multiple tumors in the stomach and small intestine by abdominal screening. All tumors were resected, and KIT gene mutations (p.Trp557Leu and p.Lys558Glu) in exon 11 were detected in all tumors and peripheral blood leukocytes. The patient was diagnosed with familial GIST. CONCLUSION: This was an extremely rare case in which familial GIST with germline KIT gene mutations co-existed with HBOC.