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Colon tumor


Invasive carcinoma arising in a colonic adenoma

Reviewers: Shilpa Jain, M.D, New York University (see Reviewers page)
Revised: 31 October 2010, last major update September 2010
Copyright: (c) 2003-2010, PathologyOutlines.com, Inc.


● Invasive only if cancer has invaded beyond muscularis mucosa into submucosa
● Can diagnose invasion without identification of submucosa if (a) marked desmoplasia, (b) infiltrative pattern, (c) ulceration or (d) clinical mass lesion


● Recommended to NOT use “carcinoma in situ” terminology in colorectum; use either high grade dysplasia or invasive carcinoma


● Present in 5% of adenomas (G Chir 2001;22:26)

Prognostic features

Recurrent disease, nodal metastases or residual local disease: 20% incidence if cancer is near margin, is poorly differentiated or if angiolymphatic invasion is present

Case reports

● Adenoma with carcinoma and mixed carcinoid-adenocarcinoma (Pathol Int 2003;53:457)
● With sarcoid reaction in regional lymph nodes (J Clin Gastroenterol 1999;28:377)
● Squamous cell carcinoma arising in villous adenoma (Hum Pathol 1988;19:362)
● Metastatic signet ring carcinoma in adenoma (Arch Pathol Lab Med 2003;127:1509)


● Polypectomy probably adequate unless margin involvement, poorly differentiated or angiolymphatic invasion (J Surg Oncol 1987;36:116, Dis Colon Rectum 2004;47:1789)

Gross images

Adenocarcinoma arising in villous adenoma

Focal carcinoma in adenoma

Micro images

Adenocarcinoma arising in tubular adenoma

Arising in villous adenoma

Metastatic signet ring adenocarcinoma in adenoma

Micro - How to Report

Report type of carcinoma, grade, presence of angiolymphatic invasion (tumor emboli in true endothelial lined channels away from tumor, not retraction artifact), status of resection margins (close to margin is within one high power field or 1-2 mm from diathermy or at diathermy), presence of dysplasia
Sample report #1: poorly differentiated carcinoma arising within an adenoma, extending to resection margin, no angiolymphatic invasion
Sample report #2: moderately differentiated carcinoma arising with an adenoma; tumor 2.5 cm from resection margin, no angiolymphatic invasion

End of Colon tumor > Polyps > Invasive carcinoma arising in a colonic adenoma

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