Malignant intestinal tumour (carcinoma of the colon), usually in the large intestine. It is one of the commonest forms of cancer, occurring equally frequently in men and women. It also is one of the most significant causes of death by cancer. Certain illnesses can cause a predisposition to carcinoma of the colon, especially a certain hereditary form of intestinal polyp in the colon, ulcerative colitis and some non-hereditary polyps. Symptoms of intestinal cancer are highly dependent on its site. A tumour in the (narrower) small intestine can cause pain through gradual obstruction, sometimes with the same clinical picture as intestinal obstruction. Sometimes the first symptom is haemorrhage or sudden loss of blood, also a symptom of tumours in the ascending (right-hand) part of the large intestine. Obstruction occurs only at a later stage, because of the width of this part of the intestine. As well as loss of blood there is persistent pain on the right, gradually becoming more severe and colic-like, and associated with malaise and loss of weight. A tumour in the last section of the large intestine causes obstruction much more quickly: the intestine is narrower and the faeces much firmer. This gives rise to pain and changes in the pattern of defecation, with gradually increasing constipation sometimes alternating with diarrhoea.