Definition / General
Very rare; by definition, no features of true invasion
Villous adenomas are also called low grade appendiceal mucinous neoplasms
Cystic adenomas are called cystadenomas (see below)
Sporadic, may be associated with colonic adenomas or familial adenomatous polyposis
Micro Description
Resemble colonic tubular, villous or tubulovillous adenomas
Cellular crowding, usually low grade dysplastic changes of nuclear elongation and stratification, pleomorphism and increased mitotic figures
Also mucin depletion
No invasion into appendiceal wall or high grade nuclear atypia
Micro Images
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Villous type adenoma
Low grade mucinous tumor with villous architecture
