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WHO Classification of Tumours
Adenoma, NOS
Small intestine


Definition

A non-invasice, benign neoplasm arising from the epithelium. It may be encapsulated or non-encapsulated. The neoplastic epithelial cells may or may not display moderate cellular atypia or dysplasia. Representative examples of adenomas are pituitary gland adenoma, follicular adenoma of the thyroid gland, and adenomas (or adenomatous polyps) of the gastrointestinal tract.

Intestinal adenoma
There is good evidence for an adenoma–adenocarcinoma sequence in the small intestine as for the colon

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Kaiser A, Jurowich C, Schönekäs H, Gebhardt C, Wünsch PH (2002)
The adenoma-carcinoma sequence applies to epithelial tumours of the papilla of Vater.
Z Gastroenterol 40: 913-20




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Sellner F (1990)
Investigations on the significance of the adenoma-carcinoma sequence in the small bowel.
Cancer 66: 702-15




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Takashima M, Ueki T, Nagai E, Yao T, Yamaguchi K, Tanaka M, Tsuneyoshi M (2000)
Carcinoma of the ampulla of Vater associated with or without adenoma: a clinicopathologic analysis of 198 cases with reference to p53 and Ki-67 immunohistochemical expressions.
Mod Pathol 13: 1300-7



. Residual adenomatous tissue at the margins is seen in 42–65% of duodenal
adenocarcinomas

Click to access Pubmed
Kaiser A, Jurowich C, Schönekäs H, Gebhardt C, Wünsch PH (2002)
The adenoma-carcinoma sequence applies to epithelial tumours of the papilla of Vater.
Z Gastroenterol 40: 913-20




Click to access Pubmed
Takashima M, Ueki T, Nagai E, Yao T, Yamaguchi K, Tanaka M, Tsuneyoshi M (2000)
Carcinoma of the ampulla of Vater associated with or without adenoma: a clinicopathologic analysis of 198 cases with reference to p53 and Ki-67 immunohistochemical expressions.
Mod Pathol 13: 1300-7



. Studies performed before the advent of advanced endoscopic techniques showed a high incidence of invasive adenocarcinoma among patients with small-bowel adenomas. For example, one study performed in 1982 reported invasive adenocarcinoma in 65% of patients with small-intestinal adenomas. More recent studies, however, demonstrate a lower incidence, which is most likely related to the now common place practice of performing upper endoscopy in patients with nonspecific symptoms. In a recent study by Catalano et al., invasive adenocarcinoma was found in only 6 out of 103 patients (5.8%) with duodenal adenomas
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Catalano MF, Linder JD, Chak A, Sivak MV, Raijman I, Geenen JE, Howell DA (2004)
Endoscopic management of adenoma of the major duodenal papilla.
Gastrointest Endosc 59: 225-32



. As a result of the widespread use of endoscopy, the earliest stages of neoplastic change have been identified and characterized in adenomas of the duodenum and peri-ampullary region.

In patients with familial adenomatous polyposis (FAP)
http://www.pubcan.org/syndrome.php?id=8 , random biopsy specimens of ileal mucosa show foci of abnormal, dysplastic crypts resembling dysplastic aberrant crypt foci of the colon in some patients, supporting the concept that, at least in patients with FAP, oligocryptal adenomas are a step in the development of epithelial neoplasms of the small intestine
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Bertoni G, Sassatelli R, Nigrisoli E, Pennazio M, Tansini P, Arrigoni A, Rossini FP, Ponz de Leon M, Bedogni G (1999)
Dysplastic changes in gastric fundic gland polyps of patients with familial adenomatous polyposis.
Ital J Gastroenterol Hepatol 31: 192-7



. Similarly, biopsy of the proximal smallintestine in a group of FAP patients showed frequent microadenomas similar to those observed in APC-knockout (Min) mice
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Preston SL, Leedham SJ, Oukrif D, Deheregoda M, Goodlad RA, Poulsom R, Alison MR, Wright NA, Novelli M (2008)
The development of duodenal microadenomas in FAP patients: the human correlate of the Min mouse.
J Pathol 214: 294-301



. In patients with FAP and in patients with sporadic adenomas, increasing grades of dysplasia are identifiable adjacent to foci of early invasive adenocarcinoma
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Kaiser A, Jurowich C, Schönekäs H, Gebhardt C, Wünsch PH (2002)
The adenoma-carcinoma sequence applies to epithelial tumours of the papilla of Vater.
Z Gastroenterol 40: 913-20



.

Although adenomas can occur throughout the small intestine, the commonest site is the ampullary and peri-ampullary region

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Schottenfeld D, Beebe-Dimmer JL, Vigneau FD (2009)
The epidemiology and pathogenesis of neoplasia in the small intestine.
Ann Epidemiol 19: 58-69



. Adenomas can be multiple, a finding that should prompt evaluation of the patient for a polyposis syndrome
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Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010



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> Histological subtypes
Tubular adenoma
Villous adenoma
Tubulovillous adenoma