[A case of colonic collision tumor (adenocarcinoma and neuroendocrine carcinoma)].

Collision tumors of the colon are rare. A 54-year-old man was referred to our hospital for the evaluation of hematochezia. Colonoscopy demonstrated the presence of about 3 cm sized mass in the rectosigmoid junction. After surgical resection, the colonic lesion was histologically composed of two discrete lesions: adenocarcinoma in the superficial layer and poorly differentiated neuroendocrine carcinoma in the deeper layer. We report this case of colonic collision tumor (adenocarcinoma and neuroendocrine carcinoma) with a review of the literature.