ABSTRACT
OBJECTIVES: To determine accurate diagnosis and proper treatment, we reviewed colonoscopic and histologic findings of flat adenoma of colon, METHODS: We studied retrospectively 2148 cases of colonoscopic findings performed in our hospital from March of 1993 to September of 1995. RESULTS: 1) The incidence of adenoma is 9.5%(203 cases), and that of flat adenoma is 1.6%(34 cases). 2) The location of flat adenoma is 3 cases in rectum(8.8%), 15 cases in sigmoid colon(44.1%), 9 cases in descending colon(26.5%), 3 cases in transverse colon(8.8%) and 4 cases in ascending colon and cecum(11.8%). 3) The diameter of flat adenoma was smaller than 5mm in 17 cases(50.0%), between 5-10mm in 8 cases(23.5%) and larger than 10mm in 9 cases (26.5%). Mean size was 9.2mm. 4) In colonoscopic features, type IIa was 25 cases (73.5%), type IIa + IIc was 5 cases(14.7%) and lateral spreading tumor was 4 cases(11.8%). 5) In histologic findings, tubular adenoma was 26 cases(76.5%), tubulovillous adenoma was 6 cases (17.6%) and serrated adenoma was 2 cases(5.9%). 6) The incidence of severe dysplasia or carcinoma was zero in smaller than 5mm, 25.0%(2 case) in 5-10mm and 55.6%(5 cases) in larger than 10mm. 7) The incidence of severe dysplasia or carcinoma was 11.5%(3 cases) in tubular adenoma and 66.7%(6 cases) in tubulovillous adenoma. 8) It was confirmed by abdominal CT scan or operation that lesions were limited to intraepithelium in 4 cases, mucosa in 2 cases submucosa in 1 case and no lymph node metastasis in any case. CONCLUSION: Even though flat adenoma of colon was smaller than polypoid adenoma, the incidence of malignant change was higher. When it was smaller than 10mm, the incidence of submucosal invasion or lymph node invasion was rare. Therefore endoscopic mucosal resection(EMR) can be the treatment of choice in flat adenoma smaller than 10mm, and after EMR, it is desirable to decide the treatment modality depending on the histologic findings.