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Colon tumor


Small early flat carcinoma of colon

Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 25 February 2012, last major update January 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Controversial entity
● In Japan, represents 6-10% of colonic cancers
● In US, small flat tumors are usually hyperplastic polyps (AJR Am J Roentgenol 2000;175:747), although adenocarcinomas do occur (Gut 2002;51:550)
● May develop from flat adenomas
● May be an important precursor of advanced malignancies (Ann Acad Med Singapore 2003;32:263)
● Tend to invade submucosa at a smaller size than polypoid lesions (Ann Pathol 2002;22:18)
● Tumors with central depression tend to rapidly invade submucosa (Société Internationale de Chirurgie 2000)

Case reports

● 52 year old man with submucosal tumor (Int J Gastrointest Cancer 2005;36:177)
● 81 year old woman with extensive nodal metastases (Int J Colorectal Dis 2001;16:262)

Gross description

● Flat, plaque like and often with central depression
● 1 cm or less
● Easier to detect with dye spraying of mucosa

Gross images

Top-flat lesion with slightly concaved surface

Micro description

● Limited to mucosa or invasive only to submucosa, by definition
● Height is usually less than twice the height of adjacent normal mucosa
● Has cytologic features of high grade dysplasia with mild architectural changes

Micro images

Invasion of submucosa


Bottom-marked submucosal invasion

Minute focus of submucosal invasion (arrow)

Molecular description

● Frequently early multiple loss of heterozygosity of 17p, 18p, 18q and 22q, coupled with LOH of other loci either simultaneously or in the early clonal progression phase (Ann Oncol 2006;17:43)

End of Colon tumor > Carcinoma > Small early flat carcinoma of colon

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