Urethral cancer classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Urethral cancer may be classified according to cell typies into 3 subtypes: transitional cell, squamous cell, and adenocarcinoma. It may also be classified into distal urethral cancer, proximal urethral cancer and urethral cancer associated with invasive bladder cancer.
Classification
Based on histology
In an analysis of Surveillance, Epidemiology, and End Results data from 1973 to 2002, the most common histologic types of urethral cancer were:
- Transitional cell (55%)
- Squamous cell (21.5%)
- Adenocarcinoma (16.4%)
Other cell types, such as melanoma, were extremely rare.
The female urethra is lined by transitional cell mucosa proximally and stratified squamous cells distally. Therefore, transitional cell carcinoma is most common in the proximal urethra and squamous cell carcinoma predominates in the distal urethra. Adenocarcinoma may occur in both locations and arises from metaplasia of the numerous periurethral glands.
The male urethra is lined by transitional cells in its prostatic and membranous portion and stratified columnar epithelium to stratified squamous epithelium in the bulbous and penile portions. The submucosa of the urethra contains numerous glands. Therefore, urethral cancer in the male can manifest the histological characteristics of transitional cell carcinoma, squamous cell carcinoma, or adenocarcinoma.
Except for the prostatic urethra, where transitional cell carcinoma is most common, squamous cell carcinoma is the predominant histology of urethral neoplasms. Since transitional cell carcinoma of the prostatic urethra may be associated with transitional cell carcinoma of the bladder and/or transitional cell carcinoma arising in prostatic ducts, it is often treated similarly to these primaries and should be separated from the more distal carcinomas of the urethra.
Based on location
Distal Urethral Cancer
These lesions are often superficial.
- Female: Lesions of the distal third of the urethra.
- Male: Anterior, or penile, portion of the urethra, including the meatus and pendulous urethra.
Proximal Urethral Cancer
These lesions are often deeply invasive.
- Female: Lesions not clearly limited to the distal third of the urethra.
- Male: Bulbomembranous and prostatic urethra.
Urethral Cancer Associated with Invasive Bladder Cancer
Approximately 5% to 10% of men with cystectomy for bladder cancer may have or may develop urethral cancer distal to the urogenital diaphragm.