Mucinous Adenoma / Cystadenoma of the Appendix
Definition
- Circumferential lining of appendiceal luminal surface by low grade dysplastic epithelium
Diagnostic Criteria
- Simple adenomatous mucinous columnar epithelium
- Focal nuclear stratification may be present
- Contains occasional goblet cells
- May be cuboidal or flat from compression
- Low grade dysplasia
- Mitotic figures, if present, are not atypical
- Must not exhibit high grade dysplasia
- No high grade cytologic features or cribriform architecture
- No invasion
- No direct invasion of muscular wall by jagged neoplastic glands
- Muscularis mucosae may be attenuated by distension making evaluation difficult
- Intramural mucin containing epithelium may be present
- No extra-appendiceal mucin with or without epithelium
- Proximal margin of appendix must not be involved
- If involved, designate as low risk of recurrence
- Sessile, usually circumferential, lining of appendiceal luminal surface
- May be undulating or villous
- Commonly associated with luminal dilation
- Common cause of mucocele
- Wall of appendix may calcify
- Specimen should be entirely submitted before this diagnosis is made
- Myxoglobulosis may be seen occasionally
- Pearl-like globules of acellular laminated mucin surrounding an amorphous granular and mucinous core
- 1-10 mm
- May calcify peripherally
- Present in lumen or periappendiceal tissue
- May be associated with colorectal adenoma or carcinoma and ovarian mucinous tumor
- Justifies consideration for screening
- Benign, does not recur after resection
- Only if all criteria are met
- If any finding is equivocal, it is best to designate as a mucinous neoplasm with low risk of recurrrence
- Not a cause of pseudomyxoma peritonei if strictly defined as above
- Usual colonic type adenomas are extremely rare
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 10/7/10
