Most adenomas of the colorectum are raised and exophytic. Some adenomas are "flat". These can be overlooked during colonoscopy, especially if small.
Gross appearance:
(1) The lesion is a slightly raised, flat, sessile plaque.
(2) It may appear reddish compared to adjacent mucosa.
(3) There may be a depressed center, especially in large lesions.
Histologic features:
(1) The dysplastic mucosa is <= 2 times the thickness of the adjacent nondysplastic mucosa.
(1) High grade dysplasia or adenocarcinoma are relatively common, especially in larger adenomas.
The presence of multiple flat adenomas may indicate that the patient has the hereditary flat adenoma syndrome, which overlaps with familial adenomatous polyposis (FAP).
To read more or access our algorithms and calculators, please log in or register.
