Urol Radiol 14:197-199 (1992)

Urologic Radiology © Springer-VerlagNewYork Inc. 1992

Urinary Bladder Leiomyoma: Magnetic Resonance Imaging Findings Menahem M. Maya and Chrystia Slywotzky Department of Radiology, Lenox Hill Hospital, New York, New York, USA

Abstract.

Benign urinary bladder tumors are very rare, leiomyoma being the most common among them. We wish to report a case and discuss the radiological findings with special emphasis on magnetic resonance (MR) imaging.

Key words: Urinary bladder, tumors -- Urinary bladder, leiomyoma -- MRI.

Case Report A 45-year-old healthy woman was found to have an incidental pelvic mass on a routine gynecological examination. The patient did not have any symptoms referable to the genitourinary tract, such as dysuria, frequency, or dyspareunia. Past medical history included a cholecystectomy performed 15 years ago. Transabdominal pelvic ultrasonography (US) demonstrated a normalsized uterus and ovaries. A well-circumscribed hypoechoic mass measuring 3.2 x 3.0 cm was found on the right posterior and inferior aspect of the urinary bladder. The mass had a predominantly intravesicle component (Fig. 1). Computed tomographic (CT) scan of the pelvis with intravenous contrast confirmed the soft tissue mass projecting into the bladder lumen (Fig. 2). No additional masses were evident. Magnetic resonance (MR) imaging of the pelvis was performed with T1- (600/15/4) and T2weighted (2500/150/2) axial, and Tl-weighted coronal images. The mass had a low-intermediate signal on Tl-weighted, and intermediate-high heterogenous signal characteristics on T2weighted sequences (Figs. 3 and 4). Small loci of lower signal intensity were observed on T2-weighted images. Subsequent cystoscopy revealed a mass lesion with intact overlying mucosa located at the edge of the right ureleral orifice. At surgery, a

Address offprint requests to: Menahem M. Maya, M.D., Department of Radiology, Lenox Hill Hospital, 100 East 77th Street, New York, NY 10021, USA

rubbery submucosalmass was dissectedand removedfrom the bladder wall with ease. Gross pathologicalinspection showed a well-circumscribed, firm, white-tantissue with interlacingbundies. Microscopic examination confirmed a spindle cell lesion consistent with a leiomyoma(Fig. 5).

Discussion Benign bladder tumors are rare. Leiomyomas are the most common with approximately 160 reported in the literature [ 1, 2]. Leiomyomas of the bladder are most commonly found in women between ages of 30 and 55. Leiomyoma of the bladder usually arises at the trigone but may be found on the lateral and posterior walls. The lesions have been classified as intravesicle (60%), extravesicle (30%), and intramural (10%). Few have intravesicle, as well as exophytic components. Extravesicle and intramural tumors usually do not cause symptoms and are detected incidentally. Intravesicle lesions may present with hematuria and/or irritation symptoms such as dysuria. Bladder outlet obstruction due to bladder neck tumors have been reported. Radiological evaluation of bladder lesions have been nonspecific. Intravenous urography usually shows fixed filling defect. US is very useful in the assessment of location of bladder lesions. Transabdominal pelvic US determines the extravesicle, intravesicle, or intramural nature of the lesion; however, it cannot distinguish masses of different origin or histology. CT, likewise, is accurate in detection of these lesions, but does not usually permit characterization. MR has been employed in recent years in preoperative staging of transitional cell neoplasms of the urinary bladder [3]. T 1-weighted images demonstrate the contrast between the low-sig-

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M.M. Maya and C. Slywotzky: Leiomyoma of the Bladder

Fig. 3. T 1-Weighted axial images show the intermediate (isointense to muscle) signal mass.

Fig. 1. Transabdominal pelvic US showing a well-circumscribed hypoechoic mass projecting into the bladder lumen.

Fig. 4. The mass has heterogenous signal with foci of high- and low-signal intensity on T2-weighted images.

Fig. 2. CT: Well-defined mass causing a filling defect in the bladder.

nal urine and moderate-intensity tumor. Determination of bladder wall invasion is made possible by the difference in T2-weighted images which contrast the high-signal tumor against the intermediate-low-signal muscle (in the bladder wall). There are only twe reports in the English language literature discussing the MR characteristics of bladder leiomyomas [4, 5]. Tomoe et al. describe a case of bladder leiomyoma similar to ours. These investigators report dot-like foci of high signal within the tumor in T2-weighted MR sequences. T2weighted images in our case showed foci of both high- and low-signal intensity. MR imaging characteristics of uterine leiomyomas have been well-

documented [6-8]. These lesions usually have medium-signal intensity on T 1-weighted images and a homogenous low-signal intensity on T2-weighted images. Degenerating leiomyomas have various appearances; medium- to high-signal on Tl-weighted and heterogenous mixed-signal on T2-weighted images. These signal characteristics have been attributed to degenerative changes, such as hemorrhage, cystic transformation, and calcification. The differential diagnosis of submucosal bladder masses includes leiomyoma, hamartoma, nephrogenic adenoma, and pheochromocytoma. MR findings in bladder pheochromocytoma have been reported and are similar to adrenal pheochromocytomas [9]. These tumors exhibit iso- or hypointense signal on T 1-weighted and markedly hyperintense signal characteristics on heavily T2-weighted sequences. Our current and a previously reported case of bladder leiomyoma have distinctive signal characteristics similar to uterine leiomyomas [4]. These characteristics may facilitate differentiating leiomyomas from the much rarer bladder pheo-

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M.M. Maya and C. Slywotzky: Leiomyoma of the Bladder

Fig. 5. Intermediate power microphotograph showing spindle cell lesion in a fascicular pattern consistent with leiomyoma.

chromocytomas. MR findings of the other lesions m e n t i o n e d in t h e d i f f e r e n t i a l h a v e n o t b e e n r e p o r t ed. I n s u m m a r y , w e r e p o r t a c a s e o f b l a d d e r l e i o m y o m a w i t h c o m p l e t e r a d i o l o g i c a l e v a l u a t i o n . M R signal characteristics may permit better characterization of submucosal bladder tumors and allow the radio l o g i s t t o suggest t h e c o r r e c t h i s t o l o g i c d i a g n o s i s , when presented with a well-circumscribed bladder wall lesion.

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References

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1. Zaffagnini V: Leiomiome della vesica. Arch Ital Uro127:184, 1954 2. Kutzman A: Leiomyoma of the urinary bladder. J Urol 37: 117, 1937 3. Rholl KS, Lee JKT, Heiken JP, et al.: Primary bladder car-

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cinoma: Evaluation with MR imaging. Radiology 163:117121, 1987 Tomoe H, Okumura T, Nakamura M, et al.: Evaluation of MR imaging of leiomyoma of bladder. Urol Int 46:349-351, 1991 Fisher M, Hricak H, Tanagho E: Urinary bladder MR imaging. Part II. Neoplasm. Radiology 157:471-477, 1985 Hricak H, TscholakoffD, Heinrichs L, et al.: Uterine leiomyomas: Correlation of MR, histopathologic findings, and symptoms. Radiology 158:385-391, 1986 Mittl RL Jr, Yeh I-T, Kressel HY: High-signal-intensity rim surrounding uterine leiomyomas on MR images: Pathologic correlation. Radiology 180:81-83, 1991 Hricak H, Finck S, Honda G, et al.: MR imaging in the evaluation of benign uterine masses: Value of gadopentetate dimeglumine-enhanced Tl-weighted images. A JR 158:10431050, 1992 Warshawsky R, Bow SN, Waldbaum RS, et al.: Bladder pheochromocytoma with MR correlation. J Comput Assist Tornogr 13:714-716, 1989

Urinary bladder leiomyoma: magnetic resonance imaging findings.

Benign urinary bladder tumors are very rare, leiomyoma being the most common among them. We wish to report a case and discuss the radiological finding...
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