Identification of APC gene mutations in jejunal carcinomas from a patient with familial adenomatous polyposis.

Jejunal carcinoma in patients with familial adenomatous polyposis has been rarely reported, and little is known about its association with genetic alterations of the APC gene. A 52-year-old woman with familial adenomatous polyposis underwent palliative resection of the proximal jejunum because of two circumferential tumors associated with peritoneal carcinomatosis. A histological examination revealed that one tumor was a poorly differentiated adenocarcinoma, and that the other was a moderately differentiated adenocarcinoma with adenomatous components. The patient did not respond to standard chemotherapy and died of disseminated disease 8 months after surgery. A genetic analysis of the APC gene identified somatic mutations in each tumor (c.4450delAG and p.R1450X) in addition to the germline mutation (c.3984del5), all of which form stop codons, resulting in truncated APC products. This report is the first description of how a second hit to the APC gene can be involved in carcinogenesis of the jejunum in familial adenomatous polyposis.