Leiomyoma of the Urethra and Bladder

Pathology Page Leiomyoma of the Urethra and Bladder eiomyomas are benign tumors of smooth muscle origin occurring throughout the genitourinary system, most commonly in the renal capsule. Bladder and urethral leiomyomas are uncommon, with approximately 200 reported cases to date. Although bladder leiomyoma accounts for less than 1% of bladder tumors, it is the most common benign soft tissue neoplasm of the bladder. The etiology and pathogenesis of these tumors are unclear, although some have hypothesized a hormonal influence, a concept supported by reports of enlargement during pregnancy and shrinkage after delivery, as well as demonstration of the presence of estrogen receptors by immunohistochemistry in 1 case.1 The majority of bladder leiomyomas occur in women in the third through sixth decades of life, with an average patient age of 44 years.2 Paraurethral or urethral leiomyomas occur almost exclusively in women and generally present as an anterior vaginal wall mass or a mass that protrudes from the urethral meatus (fig.1, A). Bladder leiomyomas may be endovesical, extravesical or intramural (fig.1, B). Endovesical tumors, which are most common, tend to cause dysuria, urgency, hematuria and sometimes flank pain. Some are pedunculated with intact overlying epithelium, and may result in bladder outlet obstruction. Intramural leiomyomas tend to be less symptomatic and are usually discovered incidentally on pelvic examination. Tumors that protrude from the urethral meatus are easily identified. Evaluation of those that present as an anterior vaginal wall mass can be aided by ultrasound, which typically demonstrates a smooth, homogeneous solid mass, or magnetic resonance imaging, which usually shows medium signal intensity on T1-weighted images and a homogeneous low signal intensity on T2-weighted images.3 Leiomyomas may appear as irregular filling defects on excretory urography or cystography, and in such cases cystoscopy is helpful (fig. 1). Bladder leiomyomas range in size from a few millimeters to as large as 30 cm, and may weigh up to 9 kg, although such great bulk is exceptional. Sectioning reveals firm, circum-

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FIG. 2. A, bladder leiomyoma composed of intersecting fascicles of smooth muscle. B, positive immunostaining for desmin.

scribed, whorled and white or tan neoplasms without hemorrhage or necrosis. Microscopically, bladder leiomyomas are similar to uterine leiomyomas, composed of fascicles of smooth muscle cells with moderate to abundant eosinophilic cytoplasm (fig. 2, A). Nuclei are oval to cigar-shaped, centrally located, blunt-ended and devoid of significant atypical changes such as hyperchromasia, pleomorphism or individual cell necrosis. Mitotic figures are absent. Immunohistochemically, leiomyomas typically exhibit strong diffuse immunoreactivity for smooth muscle actin, muscle specific actin, desmin and vimentin, and absence of immunoreactivity for cytokeratins and S-100 protein (fig. 2, B). Traditionally, treatment involves transvaginal or transabdominal excision, or in some cases endoscopic transurethral resection.4 All reported vesical and urethral leiomyomas have followed a benign biological course, with only a single reported recurrence treated by repeat excision. Howard B. Goldman, Sarah E. McAchran and Gregory T. MacLennan Glickman Urological Institute Cleveland Clinic Foundation and Department of Pathology University Hospitals of Cleveland Case Western Reserve University Cleveland, Ohio 1.

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4. FIG. 1. A, protruding urethral leiomyoma. B, leiomyoma protruding into bladder lumen (photo courtesy of Dr. Lee Ponsky, Cleveland, Ohio). 0022-5347/07/1775-1890/0 THE JOURNAL OF UROLOGY® Copyright © 2007 by AMERICAN UROLOGICAL ASSOCIATION

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Alvarado-Cabrero I, Candanedo-Gonzalez F and Sosa-Romero A: Leiomyoma of the urethra in a Mexican woman: a rare neoplasm associated with the expression of estrogen receptors by immunohistochemistry. Arch Med Res 2001; 32: 88. Goluboff ET, O’Toole K and Sawczuk IS: Leiomyoma of bladder: report of case and review of literature. Urology 1994; 43: 238. Chen M, Lipson SA and Hricak H: MR imaging evaluation of benign mesenchymal tumors of the urinary bladder. AJR Am J Roentgenol 1997; 168: 399. Cornella JL, Larson TR, Lee RA, Magrina JF and KammererDoak D: Leiomyoma of the female urethra and bladder: report of twenty-three patients and review of the literature. Am J Obstet Gynecol 1997; 176: 1278. Vol. 177, 1890, May 2007 Printed in U.S.A. DOI:10.1016/j.juro.2007.02.017