Background:
Colonic adenomatous polyps are premalignant lesions; early recognition and use of a polypectomy for these polyps can reduce the occurrence of colorectal cancer. The purposes of this study were to evaluate the complications of polypectomy and the relationship between the morphology and size of colonic polyps and their histology.
Methods:
Data on colonic polyps from 324 patients who received a polypectomy between April 1998 and December 2001 were collected. These included 207 men and 117 women, ranging in age between 17 and 86 years old, and who had had a colonoscopy or sigmoidoscopic examination. A polypectomy was performed on those colonic polyps discovered, and their morphology, size, and histology were analyzed.
Results:
The histological findings of these polyps included adenoma, carcinoma, hyperplastic, and inflammatory polyps. One and a half percent (n = 6) were carcinomas, all of which belonged to the Yamada III or IV polyp group and were more than 1 cm in size, except for 1 polyp which was 0.7 cm. One case was complicated by colon perforation, and 2 cases experienced mild bleeding with no need for a blood transfusion or hospitalization.
Conclusions:
Morphology and size are closely related to the malignant change in colonic polyps. Colonic polyps with a size greater than 1 cm and classified as Yamada type III or IV have a higher potential for malignant change, and a polypectomy should be considered when they are discovered. A polypectomy is a safe procedure with only minor complications.
(Chang Gung Med J 2003;26:339-43)

Key words:
colon polyp, polypectomy.

METHODS

Three hundred and twenty-four patients who had received a polypectomy for colonic polyps between April 1998 and December 2001 were retrospectively analyzed. The ages ranged from 17 to 86 years old. In total, 400 colonic polyps were resected either by snare polypectomy or biopsy forceps for smaller polyps. After the patients were well prepared with polyethylene glycol or magnesium citrate, the endoscope was introduced up to the cecum when performing a colonoscopy or 60 cm from the anal verge if a sigmoidoscopic examination was arranged. Once the polyps were found, they were removed by any 1 of the methods mentioned above. The retrieved polyps were sent to a pathologist for size measurement and histological review. Macroscopic appearances of the polyps were categorized according to the Yamada classification.(9)
RESULTS

Altogether, we identified a total of 400 polyps in 324 patients. The indications for colonoscopy or a sigmoidoscopic examination included hematochezia (22.5%), diarrhea (21.3%), abdominal pain (20.0%), constipation (13.8%), and other less common indications such as tenesmus, a colonic polyp history, small-caliber stool, or positive fecal occult blood (Table 1). Two hundred seventy-nine patients had a single lesion, while 28 patients had 2 lesions, and 17 patients had 3 or more lesions. The histological findings of these polyps included adenomas (73.7%), hyperplastic polyps (11.0%), carcinomas (1.5%), and others (13.8%) such as inflammation, granulation tissue, retention polyps, lipomas, juvenile polyps, and so forth (Table 2). Morphologically, the polyps could be categorized into Yamada types I to IV, that is 10.2% (41/400) were type I, 20.2% (81/400) were type II, 33.7% (135/400) were type III, and 35.7% (143/400) were type IV. Six cases of carcinoma were identified, of which 5 were Yamada type IV polyps with a size greater than 1 cm, and the other was a 0.7-cm polyp belonging to the Yamada type III group. Four of these malignant polyps had irregular surfaces, while 2 showed a smooth reddish head when viewed macroscopically by colonoscopy or sigmoidoscopy (Table 3).
One patient was complicated by colon perforation after a polypectomy for a 1.2-cm Yamada type III polyp which was later identified as being a tubular adenoma by a pathologist. Two other cases had mild bleeding after the polypectomy, but neither blood transfusion nor hospitalization was needed (Table 4).

DISCUSSION

Most studies support adenomatous polyps being neoplastic precursors of colorectal cancers.(1,10) An analysis of 7000 polyps by Shinya revealed that 2.8%, 8.4%, and 9.5% of tubular adenomas, tubulovillous adenomas, and villous adenomas contained malignant cells, respectively, which implied that colon cancerous change was directly proportional to the presence of a villous component.(2,11)
In our series, all 6 cases of cancer belonged to Yamada III or IV type , and there were no malignancies for Yamada I or II polyps. More than 95% (120/122) of polyps of Yamada types I and II were less than 1 cm in size. Apparently, size plays a very important role in predicting malignancy. Atkin et al. stated that a polyp size of 1 cm or greater had a significantly increased risk (relative risk of 3.3) of developing subsequent colorectal cancer; but those with polyps less than 1 cm did not have an increased risk of cancer.(12) Larger polyps tend to have a greater villous component and are more likely to harbor foci of carcinoma.
Carcinomas are histologically detected in 0.1% of polyps measuring less than 0.5 cm in diameter; this increases to 1.0% with 1-cm-diameter polyps and reaches 40% with polyps exceeding 2 cm.(13,14) In our study, no cancer was found in polyps of less than 0.5 cm. Only 1 polyp, 0.8% (1/120), between 0.6 and 1.0 cm contained a malignancy. The rate of malignancy increased to 7.1% (5/70) for polyps greater than 1 cm. This may imply that the risk of malignant change in polyps of less than 1 cm is very low; a polypectomy for those polyps may not be necessary, and thus the cost and complication rate of polypectomies can also be reduced. Hofstad claimed that leaving polyps up to 1 cm in diameter may be considered safe, in terms of avoiding development of invasive carcinomas, provided that annual endoscopic follow-up examinations are carried out.(15,16) Allan et al. removed a total of 1964 diminutive polyps(?0.5 cm in diameter), of which 40.7% were adenomatous and only 0.26% contained atypical cells. This further supports the chances of diminutive polyps being cancerous or containing atypical cells being very low, and that removal is not necessary for these smaller polyps.(17,18)
However, in our daily practice, we eradicate all polyps even if they are less than 1 cm to prevent adenomatous polyps from progressing to malignant transformation. Rembacken et al. reported that 63% of their lesions were polypoid, the remaining 37% were flat and depressed lesions. The overall risk of a polypoid lesion containing early cancer was 8% (17/204) compared with 14% (17/119) for flat lesions.(3) No flat lesion was discovered in our study. The possible reasons were poor preparation of the colon, and less frequent use of dye sprays. Forty-four lesions were hyperplastic polyps and were smaller lesions; some reports still reveal that dysplasia also coexists with hyperplastic polyps.(19,20)
The reported overall complication rate after a polypectomy ranges from 0.2% to 6.1%. The most common complication is bleeding, followed by transmural burn, perforation, and snare entrapment.(5-8,21,22) The incidence of complications in colonoscopic polypectomies in this series was 0.7% (3/400). Two cases were complicated by mild bleeding which improved after conservative treatment without necessity for a blood transfusion.
One perforation occurred after a polypectomy was performed for a 1.2-cm polyp which belonged to Yamada type III and was located on the descending colon. Lack of experience may have been the main cause for this. Therefore, we suggest that supervision by a senior endoscopist is mandatory when performing an endoscopic polypectomy. In conclusion, polyps greater than 1 cm and belonging to Yamada type III or IV have a higher potential for malignant change, and resection should be considered. A polypectomy is a safe procedure despite minor complications.

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From the Section of Gastroenterology, Division of Hepatogastroenterology, Department of Internal Medicine, Chang Gung Memorial Hospital, Kaohsiung.
Received: Nov. 18, 2002;
Accepted: Feb. 17, 2005
Address for reprints: Dr. Shue-Shian Chiou, Division of Hepatogastroenterology, Department of Internal Medicine, Chang Gung Memorial Hospital. 123, Dabi Road, Niaosung Shiang, Kaohsiung, Taiwan 833, R.O.C.
Tel.: 886-7-7317123 ext. 8301;
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