Mixed adenoneuroendocrine carcinoma ( collision tumor ) of the gastrointestinal tract : A case report

Mixed adenoneuroendocrine carcinomas (MANECs) of the colon are rare malignant neoplasms that mostly present at an advanced stage. MANECs can be classified as composite or collision tumors, but the neuroendocrine and exocrine component must both exceed 30% of the tumor mass. Collision tumors are composed of two distinct tumor components at the same site with a separate morphology and immunohistochemical pattern. The studies concerning MANECs are insufficient and the guidelines for the treatment of such tumors are lacking. We present a case of a 66-year-old female patient with a collision tumor of the sigmoid colon and metastases in the lymph nodes and liver.