Bladder - Papillary urothelial neoplasm of low malignant potential

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Bladder

Urothelial neoplasms-noninvasive

Papillary urothelial neoplasm of low malignant potential

Reviewer: Andreas Gaumann, Institute of Pathology Kaufbeuren, Germany

Revised: 11 June 2010, last major update June 2010

Definition

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● Resembles the exophytic urothelial papilloma, but with increased cellular proliferation exceeding the thickness of normal

urothelium; appears to lack the capacity to invade or metastasize

● ICD-O: 8130/1

Terminology

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● PUNLUMP: papillary urothelial neoplasm of low malignant potential

Epidemiology

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● Incidence of 3 cases / 100K individuals per year

● Male to female ratio 5:1, mean age 65 +/- 14 years

● In one US study, represented 25% of bladder tumors (Scand J Urol Nephrol 2008;42:237)

● In children, represent 50% of bladder tumors (BJU Int 2009 Dec 14 [Epub ahead of print])

Sites

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● Preferred sites are the lateral posterior walls and ureteric orifices

Clinical features

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● Presents with gross or microscopic hematuria

● May resemble “seaweed in ocean” at cystoscopy

● 1/3 recur, 5% as higher grade

● 10 year survival 95% or more

● Rarely associated with invasion or metastases

● Add to report "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, p53 and mitotic counts than low grade papillary carcinomas, and higher median disease free survival (76 vs. 15 months, Am J Surg Pathol 2001;25:1528)

Prognostic factors

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● Excellent prognosis when totally excised

● Tumors with focal high grade carcinoma act like high grade carcinomas

● Tumors with high Ki-67/MIB1 are more likely to recur (Cancer 2002;95:784)

Treatment

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● Resection, follow-up

Gross description (Macroscopy)

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● 1-2 cm regular polypoid tumors

Micro description (Histopathology)

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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

● Reduced cytoplasmic clearing compared to normal urothelium

● Neoplastic cells may extend down the stalk onto adjacent flat urothelium

● Mitotic figures, if present, are usually confined to basal layer

Micro images

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Series of 17 images Various images

PUNLMP (Fig A/B) compared to Orderly proliferation of urothelial cells

low grade papillary urothelial with no significant cytologic atypia.

carcinoma (Fig C/D) Papillae are well formed and lined by

urothelial cells, usually > 7 cell layers.

Umbrella cell layer often intact.

A: H&E; B: diffuse CD44+; C: superficial

CK20+ in a few cells

Cytology description

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● Slightly larger cells with irregular nuclear borders, may appear normal

Cytology images

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Fig A: papillary noninvasive neoplasm comprised of multiple layers of urothelium arranged on delicate, fibrovascular stalks; note oblong nuclei with long axes perpendicular to base of urothelium

Fig B: bladder washing shows a few clusters of urothelial cells with oval nuclei similarly arranged along their long axes (cytology diagnosis was negative)

Molecular / cytogenetics description

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● No specific changes known

Differential Diagnosis

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● Low grade papillary urothelial carcinoma: small cells more densely arranged on fibrovascular stalks, nuclear are rounder, more nuclear pleomorphism

● Papilloma: no atypia

● Polypoid / papillary cystitis: cystoscopic impression is inflammatory lesion, appears reactive at low power with inflamed background that is edematous or densely fibrous with predominantly simple, non-branching, broad-based fronds of relatively normal thickness (Am J Surg Pathol 2008;32:758)

End of Bladder > Urothelial neoplasms-noninvasive > Papillary urothelial neoplasm of low malignant potential

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