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Appendix

Carcinoma

Adenocarcinoma

Reviewer: Jaleh Mansouri, M.D. (see Reviewers page)
Revised: 21 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Clinical features
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● Rare, 0.2% of appendectomy specimens
● Usually ages 40-69 years (similar to colonic adenocarcinoma)
● 75% are symptomatic, with symptoms of acute appendicitis, abdominal mass or intestinal obstruction
● Also associated with appendiceal adenoma or rupture of appendix
● Mucinous cases typically present with pseudomyxoma peritonei
● Cases with mixed carcinoid-adenocarcinoma behave as adenocarcinoma
● Ulcerative colitis and familial adenomatous polyposis appear to confer increased susceptibility
● Patients with incidental appendiceal epithelial tumors are at risk for synchronous colonic lesions and should undergo colonoscopy

Treatment
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● Appendectomy if well-differentiated and superficial, otherwise right hemicolectomy

Case reports
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● 35 year old woman with mixed small cell carcinoma and intestinal type adenocarcinoma (Am J Surg Pathol 2004;28:1233)

Gross description
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● Cystic (cystadenocarcinoma, see below) or noncystic
● Appendix may be buried within the mass

Micro description
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● Intestinal, mucinous or signet ring cell types, invasive
● Often coexisting acute appendicitis

Micro images
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Low grade mucinous adenocarcinoma


Moderately differentiated nonmucinous adenocarcinoma


Signet ring cell carcinoma


Intestinal (colonic) type

Molecular description
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● Kras mutations in 55% (Mod Pathol 2002;15:599), 18q-, usually no microsatellite instability present

Positive stains
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● MUC2 (Mod Pathol 2003;16:403), MUC5AC (67%), CK8/18, CK13, CK19, CK20

Negative stains
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● MUC1 (usually), MUC6, CK7 (usually), CK14, p53

Differential diagnosis
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● Metastatic gastric or breast carcinoma (for signet ring types)
● Large cecal carcinomas may involve base of appendix

End of Appendix > Carcinoma > Adenocarcinoma

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