Pathology of Urinary Bladder Squamous Papilloma 

Updated: Jul 31, 2013
  • Author: Antonio Lopez-Beltran, MD, PhD; Chief Editor: Liang Cheng, MD  more...
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Definition

Squamous papilloma is a rare benign neoplasm seen in the bladder. It is composed of papillary cores with overlying histologically benign squamous epithelium. [1, 2] It is unclear whether squamous papilloma represents the squamous counterpart of urothelial papilloma.

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Epidemiology

The risk factors for squamous papilloma are similar to those for other urothelial neoplasms; cigarette smoking and occupational exposure to aromatic amines are among the most important. Specific epidemiologic studies on squamous papilloma are lacking. [1, 2]

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Etiology

Recent evidence suggests that squamous papilloma of the bladder is unrelated to human papillomavirus (HPV) infection; therefore, it seems to be unrelated to condyloma acuminatum. [1, 3]

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Location

Squamous papilloma has not been reported to have a predilection for a specific location in the bladder. Most cases arise in the dome, the lateral or posterior walls, or the bladder neck. The lesion may occur in the urethra. [1]

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Clinical Features and Imaging

Squamous papilloma most frequently occurs in elderly women. The disease follows a benign clinical course. Recurrences are uncommon. Irritative symptoms and hematuria may occur. [1]

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Gross Findings

The endoscopic appearance of squamous papilloma is identical to that of low-grade papillary neoplasms. The lesion is delicate and small or has the appearance of a polyp. [1, 2]

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Microscopic Findings

Squamous papilloma is a benign neoplasm seen in the bladder and the urethra. Histologically, it is composed of papillary cores with overlying benign squamous epithelium (see the image below). [1, 2]

Squamous papilloma of the bladder is composed of a Squamous papilloma of the bladder is composed of a delicate fibrovascular core covered by benign squamous epithelium.
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Immunohistochemistry

No or minimal basal/parabasal p53 nuclear accumulation has been reported. Epidermal growth factor immunoreactivity has been reported to occur. [1, 3, 2]

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Molecular/Genetics

Squamous papilloma is a DNA-diploid lesion; it tests negative for HPV DNA. [1]

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Tumor Spread and Staging

TNM stage Ta applies (ie, squamous papilloma is noninvasive). As a benign lesion, it does not spread out. [1, 2]

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Prognosis and Predictive Factors

Squamous papilloma is a benign tumor that may rarely recur but does not progress. Some patients may in time develop bladder cancer. [1] In a recent study that included 5 patients with squamous papilloma, 1 patient had low-grade urothelial carcinoma at cystectomy after an interval of 21 months (low-grade urothelial carcinoma preceded the diagnosis of squamous papilloma); 2 patients were free of lesions on follow-up biopsy. Two cases were lost to follow-up. [3]

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