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Colon tumor

Polyps

Tubular adenoma


Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 23 October 2011, last major update August 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features
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● 90% of GI tubular adenomas occur in colon; also stomach and small intestine
● 50% are single
● Prevalence of 30% in adults at autopsy, increasing with age
● Risk of subsequent adenomas or colorectal carcinoma is related to size; higher risk if 6-10 mm or larger, multiple adenomas or family history (Ann Intern Med 1998;129:273, Gut 2002;51:424)
● May bleed due to twisting; large polyps may cause change in bowel habits or intussusception
● Associated with hypertriglyceridemia (World J Gastroenterol 2006;12:1261)

Case reports
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● Osseous metaplasia in adenoma of 85 year old woman (J Clin Pathol 2005;58:220)
● Metastatic signet ring cell carcinoma in adenoma (Pathol Res Pract 2004;200:707, Arch Pathol Lab Med 2003;127:1509)
● Metastatic melanoma in adenoma of 85 year old man (Dis Colon Rectum 2002;45:1681)
● Coexisting multifocal MALT lymphoma (Int J Colorectal Dis 2011;26:1221)

Gross description
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● Usually < 1 cm and pedunculated, but may be sessile
● Darker color than surrounding mucosa
● Multiple polyps tend to cluster

Gross images
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Tubular adenoma


Hemorrhagic surface


Multiple cecal polyps

Micro description
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● Increased number of glands and cells per unit area compared to normal mucosa
● Cells are crowded with hyperchromatic nuclei, increased mitoses (some atypical)
● Mucin production usually decreased
● Changes first affect superficial portion of glands
● Dysplasia from mild to severe (carcinoma in situ)
● Rarely biotin-containing clear nuclei, squamous metaplasia (J Surg Oncol 1984;26:130), Paneth cells, endocrine cells, malakoplakia
● Clear cell change (Histopathology 1999;34:250) may be precursor to clear cell adenocarcinoma (Am J Surg Pathol 2010;34:1344)
● Pseudocarcinomatous invasion: submucosal displacement and dilated adenomatous glands may mimic carcinoma (Nihon Shokakibyo Gakkai Zasshi 2011;108:458, Gut Liver 2009;3:130)

Micro images
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Tubular adenoma


Compared to normal mucosa


With osseous metaplasia

   

Pseudocarcinomatous invasion

Virtual slides
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Tubular adenoma

Positive stains
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● bcl2 (almost all cases), increased CEA (in atypical areas)

Negative stains
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● p53 (usually)

Molecular description
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● 1/3 are aneuploid
● Depending on the villous component, two types of tubular adenomas can be identified (Am J Surg Pathol 2011;35:212):
TA1: less than 1% villous component, lower rate of p53 overexpression, Kras mutation and MGMT loss
TA2: 1-20% villous component, higher rate of p53 and Kras mutation and MGMT loss

End of Colon tumor > Polyps > Tubular adenoma


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