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WHO / ISUP classification


Reviewers: Sean Williamson, M.D. (see Reviewers page)
Revised: 2 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.

Prior classification systems

● Ash (1940): classify as transitional cell carcinoma grades 1-4; grade 1 comparable to papilloma, grade 2 comparable to low grade; grade 3 (most) and 4 comparable to high grade
● Mostofi (1960): grade 1 called papilloma and not carcinoma


● World Health Organization / International Society of Urologic Pathologists consensus classification that is controversial for some lesions (low malignant potential)
● Major changes from prior systems are that papillary urothelial carcinomas must exhibit atypia and carcinoma in situ need not be full thickness
● WHO/ISUP grade correlates with tumor stage and recurrence
● Website tutorial (click here), has further discussion; free but requires registration


● Flat mucosa without overt increase in thickness (usually normal urothelium considered 3-7 cell layers, depending on degree of distension)
● Includes a spectrum of slight disorganization of cells and nuclear pleomorphism that formerly might be considered mild dysplasia
● Size of normal urothelial cells is 3x lymphocytes

● Flat or papillary

Flat lesions with atypia:
● Reactive
● Unknown significance
● Dysplasia (low-grade intra-urothelial neoplasia)
● CIS (high-grade intra-urothelial neoplasia)

Papillary urothelial neoplasms:
● Papilloma
● Inverted papilloma
● Papillary urothelial neoplasm of low malignant potential (PUNLMP)
● Low-grade papillary urothelial carcinoma
● High-grade papillary urothelial carcinoma

Invasive urothelial neoplasms:
● Lamina propria invasion
● Muscularis propria invasion (for bladder)

Low-grade neoplasms:
● Includes papilloma
● Inverted papilloma
● Papillary urothelial neoplasm of low malignant potential (PUNLMP)
● Low grade papillary urothelial neoplasms (urothelial carcinoma grades 1/3 and some grade 2/3)

End of Ureters > WHO / ISUP - general

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