The malignant potential of freshly developed colorectal polyps according to age.
BACKGROUND
Although malignant colorectal neoplasms are found more frequently in older population, polyps found at one-time colonoscopy may be a mixture of lesions that developed at various earlier ages. Newly developed adenomas found at the follow-up colonoscopies will reflect the exact relation between malignant potential and the age of development of colorectal polyps.


METHODS
The results of 44,065 follow-up colonoscopies on 11,912 subjects were analyzed. The proportion of invasive cancer or high-grade dysplasia among all neoplasms, "proportion of malignancy," was evaluated in relation to age groups (young: <50 years old; middle: 50-59 years old; and old: >or=60 years old).


RESULTS
At the follow-up colonoscopies, a total of 8,271 newly developed neoplasms were found, of which 41 (0.50%) lesions were malignant. The proportion of malignancy was 0.35%, 0.31%, and 1.07% in the young, middle, and old age groups, respectively (P(trend) = 0.002). This trend remained significant when stratified by the size of polyps. The proportion of malignancy was higher on the left-side colon than on the right-side colon, except in the old age group, where it was similar on either side. The proportion of malignancy at the follow-ups was not associated with the lesions found at the initial colonoscopies.


CONCLUSIONS
The development of malignant lesions in small sizes increased on the colon or rectum at older ages.
Yamaji
Yutaka
Y
Department of Gastroenterology, University of Tokyo, 7-3-1 Hongo, Tokyo 113-8655, Japan. yamaji-tky@umin.ac.jp
Mitsushima
Toru
T
Yoshida
Haruhiko
H
Watabe
Hirotsugu
H
Okamoto
Makoto
M
Wada
Ryoichi
R
Ikuma
Hitoshi
H
Kawabe
Takao
T
Omata
Masao
M
D000230:Adenocarcinoma / Q000453:epidemiology / Q000473:pathology*; D000236:Adenoma / Q000453:epidemiology / Q000473:pathology*; D000367:Age Factors; D003111:Colonic Polyps / Q000473:pathology*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged