Background and study aims: Serrated adenomas are a distinct form of colorectal neoplasia. Several reports have indicated that serrated adenomas may give rise to invasive adenocarcinoma. The present study describes the endoscopic findings in 54 colorectal serrated adenomas detected in 35 patients.
Patients and methods: Thirty-five of 1225 patients (2.9%) who underwent colonoscopy during 1993 in the gastrointestinal endoscopy section at Karolinska Hospital (22 men, 13 women; mean age 68 years, range 49-84 years) were found to have a total of 182 polyps, including 118 adenomas and 64 hyperplastic polyps at histopathology. Fifty-four of the 118 adenomas (46%) were of the serrated type. In two of the 35 patients, two large exophytic colorectal adenocarcinomas were also present.
Results: Twenty-nine of the serrated adenomas (53.5%) were flat, 23 were sessile (42.5%), and two were pedunculated (4%). The mean sizes of the flat and sessile lesions were 3.5 mm (range 2-10 mm) and 5.9 mm (range 2-20 mm), respectively. The endoscopic appearance of serrated adenomas of 5 mm or less (n = 39, 72%) was similar to that of hyperplastic polyps. Forty-two (78%) of the lesions were located in the sigmoid and rectum. Fifty-one lesions showed low-grade dysplasia (including one with microinvasive carcinoma), and the remaining three had high-grade dysplasia.
Conclusions: The study suggests that small polyps with a hyperplastic appearance should not be regarded as innocuous, since they may represent serrated adenomas carrying a malignant potential.