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Bladder

Urothelial neoplasms-noninvasive

Urothelial papilloma

Reviewers: Monika Roychowdhury, M.D., University of Minnesota Medical Center (see Reviewers page)
Revised: 15 May 2011, last major update May 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Definition
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● Discrete papillary growth with a central fibrovascular core lined by urothelium of normal thickness and cytology

Epidemiology
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● Uncommon if use restrictive diagnostic criteria (less than 1% of bladder tumors)
● Tends to occur in younger patients (mean age, 46 years; range 22-89 years) and may occur in children (Cancer 1999;86:2098)
● Risk factors similar to those of urothelial neoplasm (cigarette smoking and occupational exposure to aromatic amines, Histopathology 2008;53:621)

Sites
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● Most common in posterior or lateral walls (close to ureteric orifices) and urethra

Clinical features
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● Hematuria
● Either de novo (most common) or secondary to known urothelial carcinoma
● In de novo cases, mean age 46-58 years, 2/3 male, occasional recurrence, occasional progression to papillary urothelial carcinoma
● In secondary cases, mean age 66 years, may recur
● Recommended to avoid labeling these patients as having cancer (Am J Surg Pathol 2004;28:1615)
● Benign behavior; may recur but only rarely progresses

Prognostic factors
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● Rare cases of progression have been described in association with immunosuppressive therapy

Treatment
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● Excision and follow-up

Gross description (Macroscopy)
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● Soft, pink, small isolated growth with delicate papillary structures, usually pedunculated, mean 3 mm

Micro description (Histopathology)
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● Discrete papillary fronds with occasional branching but without fusion; these fronds are covered by normal urothelium
● Papillae appear to float above urothelial surface due to sectioning of branching papillae
● Papillae usually small with scant stroma and slender fibrovascular cores
● May have large papillae with marked stromal edema or cystitis cystica-like invaginations
● Lined by normal appearing urothelium with prominent umbrella cells, normal polarity, variable dilated lymphatics within fibrovascular fronds, vacuolization; no hyperplasia, no dysplasia, no fusion of adjacent fronds, no necrosis, no/minimal mitotic figures (if present, they are in basal layers)
● Rarely urothelial papilloma can extensively involve the mucosa, a phenomenon referred to as diffuse papillomatosis (Eur Urol 2004;46:170)

Micro images
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Series of 12 images with discrete papillary fronds lined by normal urothelium

           
Low power

           
Papilloma with delicate fibrovascular core, normal urothelium and cystoplasmic vacuoles


Papilloma with simple, nonbudding papillary architecture, slender papillae with thin fibrovascular cores


A: complex, budding papillary pattern; B: anastomosis of individual papillae


Large fibrovascular cores with prominent edema


Prominent umbrella cell layer


CK44 and CK20

Positive stains
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● CK20 (limited to superficial/umbrella cells as in normal urothelium)

Negative stains
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● p53

Molecular / cytogenetics description
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● Diploid; has frequent FGFR3 mutations (seen in 75% of cases, J Pathol 2002;198:245)

Differential diagnosis
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● Papillary urothelial neoplasm of low malignant potential: longer and thicker papillae with hyperplasia, less prominent umbrella cells
● Papillary urothelial hyperplasia: >7 cells thick, undulating pattern of thin mucosal papillary folds of varying heights, no discrete fibrovascular cores, vascularity present at base of urothelial proliferation

Additional references
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● Mod Pathol 2003;16:623, J Clin Pathol 2008;61:3

End of Bladder > Urothelial neoplasms-noninvasive > Urothelial papilloma

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