Primary coexisting adenocarcinoma of the colon and neuroendocrine tumor of the duodenum: A case report and review of the literature.

Background: Neuroendocrine tumors (NETs) arise from the body's diffuse endocrine system. Coexisting primary adenocarcinoma of the colon and NETs of the duodenum (D-NETs) is a rare occurrence in clinical practice. The classification and treatment criteria for D-NETs combined with a second primary cancer have not yet been determined.

Case summary: We report the details of a case involving female patient with coexisting primary adenocarcinoma of the colon and a D-NET diagnosed by imaging and surgical specimens. The tumors were treated by surgery and four courses of chemotherapy. The patient achieved a favorable clinical prognosis.

Conclusion: Coexisting primary adenocarcinoma of the colon and D-NET were diagnosed by imaging, laboratory indicators, and surgical specimens. Surgical resection combined with chemotherapy was a safe, clinically effective, and cost-effective treatment.