Metachronous primary colon and periampullary duodenal cancer: A case report.

RATIONALE: Primary periampullary duodenal cancer accounts for 3% to 17% of periampullary cancers. There are no previous reports of metachronous primary colon and periampullary duodenal cancer. PATIENT CONCERNS: We present a case of primary periampullary duodenal cancer that occurred metachronously after colon cancer. DIAGNOSES: Imaging and endoscopic examinations, serum tumor marker levels, and pathology confirmed metachronous colon and periampullary duodenal cancer, with 14-month interval between the diagnoses of the 2 malignancies. INTERVENTION: The patient received right hemicolectomy combined with mFOLFOX6 chemotherapy for colon cancer and pancreatoduodenectomy for periampullary duodenal cancer. OUTCOMES: The patient has been followed up for 6 years since the pancreatoduodenectomy and shows no signs of recurrence or metastasis. LESSONS: The risk of developing a second malignancy may be associated with the site of the first tumor. Patients with right colon cancer may have particularly high risk of developing small intestinal cancer, including duodenal cancer. Early detection and active surgical treatments can improve prognosis. Long-term regular follow-up is necessary to detect new malignancies occurring after the diagnosis colon cancer.