Differential diagnosis of dysplasia-associated lesion or mass and coincidental adenoma in ulcerative colitis

PURPOSE: This study was undertaken to investigate factors that influenced differential diagnosis of dysplasia-associated lesion or mass and coincidental adenoma in patients with ulcerative colitis. METHODS: Among 346 patients with ulcerative colitis who underwent colonoscopy between 1979 and 1995, 27 patients had macroscopic neoplastic lesions and were divided into two groups: those with dysplasia-associated lesion or mass (16 patients) and those with adenoma (11 patients), each being categorized by the presence and absence of dysplasia in the hat mucosa adjacent to the elevated lesions, respectively. RESULTS: Thirteen of 27 patients had dysplasia-associated lesion or mass detected by colonoscopic biopsy; 10 of these patients underwent colectomy, and all had dysplasia-associated lesion or mass in the colectomy specimens. Two patients whose biopsy findings were adenoma had an unsuspected dysplasia-associated lesion or mass in the operative specimens. In the remaining 12 patients, the macroscopic lesions were excised during colonoscopy because of clinical and colonoscopic evidence of adenoma. One of them was proved to have dysplasia-associated lesion or mass, and the other 11 were confirmed as having adenoma in the polypectomy specimens. Patients with dysplasia-associated lesion or mass were significantly younger (P < 0.05), had longer duration of ulcerative colitis (P < 0.01), and had more extensive disease (P < 0.005) than those with adenoma. The colonoscopic appearance was plaque-like in 13, sessile in 13, and pedunculated in 2 of the 28 lesions with dysplasia-associated lesion or mass, whereas it was plaque-like in only 1 and sessile or pedunculated in 15 of the 16 lesions with adenoma (P < 0.001). The mean size of the lesions that were considered to be dysplasia-associated lesions or mass and adenoma was 1.8 and 0.5 cm, respectively (P < 0.0001). CONCLUSIONS: Colonoscopic biopsy for detection of dysplasia in the flat mucosa adjacent to macroscopic neoplastic lesions is an appropriate preoperative approach to distinguish dysplasia-associated lesions or mass from adenomas in patients with ulcerative colitis. The statistically significant variables that influenced the differential diagnosis were age, duration of disease, extent, tumor size, and tumor colonoscopic appearance.