Ureters - Papillary urothelial neoplasms

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WHO/ISUP classification

Papillary urothelial neoplasms – not carcinoma

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

Papilloma

General
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● Rare, benign, usually small and isolated in younger patients
● May recur

Gross description
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● Soft, pink, delicate papillary structures, usually pedunculated

Micro description
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● Distinct papillary growth
● Small delicate stalk with central fibrovascular core lined by urothelium of normal thickness and cytology
● No fusion of adjacent fronds
● Papillary fronds may appear detached due to sectioning of complex arborizing papillary structures
● Necrosis rare
● Minimal mitosis

Micro images
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Urothelial papilloma: H&E, CD44, CK20

Additional references
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● Mod Pathol 2000;13:1315

Inverted urothelial papilloma

General
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● Adult and elderly men
● Low risk of recurrence if completely excised
● May be associated with urothelial carcinoma, rarely in the inverted urothelial papilloma itself

Gross description
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● Usually solitary, polypoid, pedunculated
● At trigone, bladder neck or prostatic urethra

Micro description
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● Invagination of epithelium, no atypia, no papillae, minimal stroma
● Epithelium may be insular, trabecular, pallisading, gland-like resembling cystitis glandularis
● Rarely neuroendocrine

Differential Diagnosis
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● Urothelial carcinoma with inverted growth pattern: abnormalities of #3, #7, #17 and 9p21 by FISH frequently present; positive for MIB-1/Ki-67, p53, CK20 by immunohistochemistry (Am J Surg Pathol 2007;12:1861)

Papillary urothelial neoplasm of low malignant potential

General
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● May arise in young patients
● 1/3 recur, 5% as higher grade
● 10 year survival 95% or more
● Are rarely associated with invasion or metastases
● Some question distinguishing these lesions from low-grade papillary urothelial carcinomas
● Patients with these tumors are at risk of developing new bladder tumors ("recurrence"), usually of a similar histology; however, since these subsequent lesions occasionally manifest as urothelial carcinoma, follow up is warranted
● Have lower MIB-1/Ki-67, p53, mitotic counts than low-grade papillary carcinomas, and higher disease free survival (76 vs. 15 months, Am J Surg Pathol 2001;25:1528)

Micro description
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● Orderly arrangement of cells within papillae with minimal architectural abnormalities and minimal nuclear atypia, regardless of cell thickness
● Thicker epithelium than papilloma, increase in nuclear size and hyperchromasia compared to papilloma
● Mitotic figures if present are usually confined to basal layer

Micro images
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Various images

Additional references
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● Mod Pathol 2001;14:267, Mod Pathol 2000;13:1315

End of Ureters > WHO/ISUP classification > Papillary urothelial neoplasms – not carcinoma

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