Can ulcerative colitis transform into cancer ? all of cases or in some ?

In theory all, but..: If left alone long enough, it is thought that most or all will turn in to cancer over the course of many years of active disease. There are however many factors such as the disease activity, response to ; type of treatment, amount of mucosa at risk, and genetic predisposition. Best to see a colorectal surgeon or GI doctor who has a special interest and experience with inflammatory bowel disease.

Risk factor: Uc is a risk factor for colon cancer. See more detailed information here: http://digestive.Niddk.Nih.Gov/ddiseases/pubs/colitis/#cancer.

Yes indeed: After a few years, the risk of developing an adenocarcinoma makes it worth biopsying frequently. A pathologist can tell when there is enough abnormal change in the cells that line the colon to justify taking it out to prevent an actual cancer from forming. How often this happens depends on the severity of the ulcerative colitis; overall it's about 20% at 30 years.