0022-5347/05/1741-0312/0 THE JOURNAL OF UROLOGY® Copyright © 2005 by AMERICAN UROLOGICAL ASSOCIATION
Vol. 174, 312, July 2005 Printed in U.S.A.
Pathology Page TUMORS OF THE MALE URETHRA The male urethra is divided into prostatic, membranous and penile segments. The prostatic portion is lined by transitional epithelium. The membranous and penile portions are lined by pseudostratified or stratified columnar epithelium. Squamous epithelium lines the fossa navicularis and may be found focally throughout the penile urethra. Ejaculatory ducts empty into the prostatic urethra, whereas secretions from Cowper’s glands and paraurethral glands of Littre´ enter the membranous and penile urethral segments, respectively. Tumors of the male urethra can be subclassified as nonneoplastic and neoplastic. The most common nonneoplastic tumors are condyloma acuminatum and urethral polyps. Condyloma acuminatum accounts for approximately 30% of male urethral tumors, typically occurring in men 20 to 40 years old. It is a proliferative squamous lesion associated with human papillomavirus infection, most frequently type 6 or 11. It is considered to be a reactive process rather than a neoplasm. Condyloma acuminatum develops slowly and is usually asymptomatic but may cause urethral bleeding. Grossly, the lesions are flat or papillary (fig. 1). Histologically, the hallmark feature of condyloma acuminatum is koilocytic change, characterized by squamous cells with wrinkled, raisinoid nuclei with perinuclear halo formation due to cytoplasmic retraction (fig. 1). Urethral polyps are most commonly categorized as fibrous or prostatic. Fibrous polyps are congenital and present early in life (infants and boys 3 to 10 years old) with symptoms of obstruction, hematuria or urinary tract infections. Grossly, the lesion is a polypoid tumor with a narrow stalk that originates at or near the verumontanum. Histologically, the polyp is lined by transitional epithelium and the stroma is
composed of connective tissue and blood vessels. Prostatic polyps are of uncertain etiology but most are probably reactive proliferations arising secondary to urethral injury. Like fibrous polyps, prostatic polyps are usually based near the verumontanum but prostatic polyps present at a later age (13 to 31 years) with symptoms of obstruction, hematuria or hemospermia. Grossly, the lesion is a sessile polypoid or papillary tumor. Histologically, it consists of prostatic acini lined by double-layered prostatic type epithelium and arranged to form polypoid nodules or papillary structures. Primary urethral neoplasms account for less than 1% of genitourinary tumors in males. The most common neoplastic tumors of the urethra are similar to those of the bladder, and include squamous cell carcinoma, urothelial carcinoma and adenocarcinoma. Squamous cell carcinoma is the most common urethral carcinoma in men, and generally involves the bulbomembranous or pendulous portions of the urethra (fig. 2). Transitional cell carcinoma, although predominantly found in the prostatic urethra, rarely may be distally located, and adenocarcinoma tends to involve the bulbomembranous urethra. Grossly, these tumors are irregular masses projecting into the urethra and they may be ulcerated. The histological features of these neoplasms are not distinctive, as they are similar to those noted in such tumors found in other sites. The distal urethra is the most common site in the genitourinary tract for the development of a primary melanoma. Grossly, these lesions can be flat or nodular, and may or may not be pigmented. Histologically, although some urethral melanomas resemble their cutaneous counterparts, others can be diagnostically challenging due to absence of pigment or the presence of papillary or spindle cell morphology. Urethral melanomas have a poor prognosis, and patient survival beyond 5 years is uncommon. Stacy J. Kim and Gregory T. MacLennan Institute of Pathology University Hospitals of Cleveland Case Western Reserve University Cleveland, Ohio
FIG. 1. Condyloma acuminatum of urethra. Urethroscopy image courtesy of Dr. Martin I. Resnick, Cleveland, Ohio.
FIG. 2. Squamous cell carcinoma of urethra. Reprinted with permission from MacLennan G. T., Resnick, M. I. and Bostwick, D. G.: Pathology for Urologists. Philadelphia: W. B. Saunders Co., 2003.