대한대장항문학회

Purpose : A laterally spreading tumor (LST) has its own characteristic features and growth<br>pattern. Information about LST is scanty in Korea, therefore this study was designed in order<br>to contribute to the literature. Methods : In this study, 43 patients with LSTs were included.<br>The diagnoses were made by colonoscopy in all cases. Treatment options included endo<br>scopic resection, transanal excision, and surgical resection. In reviewing and analyzing the<br>cases, we made a special emphasis on size, classification, histology, and treatment. Results:<br>The most frequent location was the rectum, followed by the sigmoid colon and the ascending<br>colon in that order. Lesions smaller than 20 mm accounted for 69.8%. Granular homogeneous<br>LSTs, 41.9%. Lesions larger than 20 mm, except granular homogeneous LSTs, showed an<br>abrupt increase in malignancy rate. Tubular adenomas accounted for 65.1%. The overall<br>malignancy rate was 20.9%, and the submucosal cancer rate, 9.3%. There were no<br>malignancies in the granular homogeneous LSTs. The malignancy rate for the mixed-nodule<br>type lesions was 33.3% (4/12), and the nongranular LSTs, 38.5% (5/13). Polypectomy was<br>done in 37.2% of the lesions, endoscopic mucosal resection (EMR) in 16.3%, and endoscopic<br>piecemeal mucosal resection (EPMR) in 16.3%. The overall endoscopic resection rate was<br>83.7% (36/43). EMR was applicable to lesions smaller than 20 mm, and EPMR to those larger<br>than 20 mm. Transanal resection was done in 2 cases with lesions. Five cases were resected<br>surgically. Four of them were submucosal invasive lesions, and one, a mucosal lesion which<br>was wide and had initially been thought to be a submucosal cancer. There were two<br>recurrences during the average 15-month follow-up period. The follow-up rate was 81.4%<br>(35/43). Of these 2 recurring cases, one patient was treated endoscopically and the other,<br>transanally. Conclusions: LSTs show different behavior depending on the endoscopic classi<br>fication. Granular homogeneous LSTs are seldom larger than 30 mm and are good candi<br>dates for endoscopic treatment. The mixed-nodule type and the nongranular type show a<br>marked predisposition to malignancy when they are over 20 mm, and nongranular-type LSTs<br>have a higher rate of submucosal invasive cancers. Thus, in the cases of the mixed- nodule<br>and nongranular types, careful consideration should be given for deciding between endoscopic<br>treatment and surgical resection. Complete resection should be assured to prevent recurrence,<br>and follow-up surveillance is required in all lesions for more than 3 to 5 years.<br>