Dysplasia seen in biopsies in longstanding ulcerative colitis is an indication of a risk of cancer. The dysplasia can either be flat, and not detectable during endoscopy, or associated with a visible lesion or mass, polypoidlike. This kind of dysplasia is called "Dysplasia Associated Lesion or Mass".

While only dysplasia without any cancer is seen in biopsies fron the visible lesion, a DALM is a significant indication of an invasive cancer in other parts of the colon. In the series of MO Blackstone, 7 out of 12 patients with DALM, 7 patients were found to have cancer. In only 2 of the 7 patients the dysplasia in the biopsies was graded as severe, in the other 5 only mild or moderate. A DALM-finding thus is a strong indication for colectomy. (Blackstone MO, Riddell RH, Rogers BH, Levin B. Dyplasia-associated lesion or mass (DALM) detected by colonoscopy in longstaning ulcerative colitis: an indication for colectomy. Gastroenterology, 80(2): 366-74, 1981)