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Appendix

Benign tumors

Mucinous cystadenoma

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

General
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● Most common mucinous neoplasm of appendix
● Also called low grade appendiceal mucinous neoplasm, especially if associated with pseudomyxoma peritonei
● May be associated with ovarian mucinous cystadenoma and colonic neoplasms
● May present with pain due to distention, symptoms of acute appendicitis, pseudomyxoma peritonei or as abdominal mass
● May represent a continuum with noncystic adenomas
● Peaks in 60’s (age)
● When associated with diverticula (30-40% of time), may cause pseudomyxoma peritonei (Mod Pathol 2000;13:495)
● Sample thoroughly to rule out malignancy
● If spreads beyond appendix, survival rates were 100%, 86% and 45% at 3-, 5- and 10- years on one study (Am J Surg Pathol 2003;27:1089)

Case reports
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● 54 year old woman with mucinous cystadenoma of pancreas and appendix (JOP J Pancreas 2004;5:97)

Treatment
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● Excision
● Low recurrence rate if low grade features and confined to appendix

Gross description
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● Variable cystic luminal dilation, usually filled with viscid mucus
● 20% perforate appendix
● Mucin often attached to serosa or free in peritoneal cavity

Micro description
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● Usually intestinal type epithelium (crowded columnar cells with basal, elongated, hyperchromatic nuclei, often with large amounts of apical mucin)
● Dysplastic changes often minimal but greatest at crypt bases
● High grade dysplastic changes less common
● Villous adenomas may completely replace appendiceal mucosa
● May resemble serrated adenoma (mixed hyperplastic polyp and adenoma) or borderline ovarian mucinous tumor
● Occasionally see foreign body giant cell reaction, granulation tissue, chronic inflammation, fibrosis, calcification, displaced epithelium or mucin within muscularis propria
● Muscularis mucosa may be thin/absent and replaced with hyalinization / fibrosis
● Rarely heterotopic bone formation (Arch Pathol Lab Med 1996;120:666)

Micro images
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Intestinal type epithelial lining


Lined by pseudostratified columnar cells with low grade dysplastic changes

     
Involving diverticulum

Negative stains
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● CK7 (usually)

Differential diagnosis
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● Retention cyst or simple mucocele (usually < 1 cm, no neoplastic epithelium despite extensive sampling), invasive adenocarcinoma (infiltrative pattern, desmoplastic stroma)

Additional references
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● Hum Pathol 1997;28:1039, Am J Surg Pathol 2001;25:1095

End of Appendix > Benign tumors > Mucinous cystadenoma

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