Background: The management of low-grade (LGD) and indefinite dysplasia (IND) in patients with ulcerative colitis (UC) remains controversial, as outcomes after a diagnosis of LGD or IND in previous studies vary widely.

Methods: All patients evaluated were from a single institution referral center who had a history of UC and a diagnosis of either LGD or IND between 1994 and 2008 as confirmed by 2 expert gastrointestinal (GI) pathologists. Data were collected by chart review of electronic and paper medical records. All patients who did not undergo a colectomy within 90 days of their dysplasia diagnosis were included in the final analysis. Hazard ratios for risk factors as well as incidence rates and Kaplan-Meier estimates were used to calculate the progression to high-grade dysplasia (HGD) or colorectal cancer (CRC).

Results: Thirty-five patients were included in the analysis, of whom 2 patients with IND and 2 patients with LGD developed HGD or CRC over a mean duration of 49.8 months. In total, the incident rate for advanced neoplasia for all patients was 2.7 cases of HGD or CRC per 100 person-years at risk. For flat and polypoid LGD the incident rate of advanced neoplasia was 4.3 and 1.5 cases per 100 person-years at risk, respectively. Patients with primary sclerosing cholangitis (PSC) had an incident rate of 10.5 cases per 100 years of patient follow-up.

Conclusions: We report a low rate of progression to HGD or CRC in patients who underwent surveillance for LGD or IND; polypoid dysplasia showed less risk of progression than flat dysplasia.