Abstract
Tumors that have both neuroendocrine and exocrine components in the gastrointestinal system are rare. One of the rarest places in the gastrointestinal system is the colon. These tumors are called mixed adenoneuroendocrine carcinomas (MANEC). To diagnose MANEC, the neuroendocrine and exocrine components that make up the lesion must be present at least 30%. A 70-year-old female patient with complaints of abdominal distension, malnutrition, nausea, and vomiting was admitted to our clinic from another center. The patient underwent blood tests, whole abdominal tomography, and colonoscopy. Right hemicolectomy and retroperitoneal lymph node dissection were performed with the preliminary diagnosis of colon cancer. Histopathological diagnosis was MANEC, and tumor stage was T3N1M0. Adjuvant chemotherapy was applied. Although MANEC is rare, it is a difficult and complex cancer to diagnose due to its nonspecific features. Diagnosis is made with histopathological and immunohistochemical evaluation along with clinical suspicion. Treatment is surgery and adjuvant therapy.