Rectal cancer. Colonoscope (endoscope) view of a carcinoid tumour in a patient's rectum. This is a malignant tumour (neoplasm) that arises in the mucosa of the gastrointestinal tract. This type of cancer readily spreads (metastases) especially to lymph nodes. The prognosis for patients with metastases is very poor. If diagnosis is made earlier, surgical removal and anticancer drugs can cure the condition, as in this case.