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CASE REPORT
Primary leiomyoma of the bladder radiologically mimicking
a retroperitoneal tumor - a case report
Mami Taniuchi1, Masato Yanagi1, Tomonari Kiriyama2, Jun Akatsuka1, Hiroya Hasegawa1, Hikaru Mikami1, Yuki Endo1,Hayato Takeda1, Yuka Toyama1, Go Kimura1, and Yukihiro Kondo1
Department of Urology, Nippon Medical School Hospital, Tokyo, Japan, 2Department of Radiology, Nippon Medical School Hospital, Tokyo,
Japan1

Abstract : The case presented is of a 47-year-old patient with an extravesical pedunculated bladder leiomyoma,
which was difficult to distinguish from a retroperitoneal tumor. Preoperatively, it was suspected to be a retroperitoneal tumor and a laparotomy with tumor resection was performed. lntraoperatively, the bladder and tumor were connected by a cord-like tissue. A retrospective review of preoperative images revealed that cord-liketissue, identified intraoperatively, was also present. Bladder leiomyomas can grow as extravesical pedunculated
tumors. Therefore, when the continuity between the bladder and tumor is only a cord-like object, the finding ofcontinuity is useful to diagnose with bladder leiomyoma. J. Med. Invest. 70 : 513-515, August, 2023
Keywords : Primary leiomyoma, bladder tumor, retroperitoneal tumor

CASE RRESENTATION
A 47-year-old man (height, 177 cm ; weight, 82 kg ; body massindex, 26.2 kg / m2) presented with hypertension, tachycardia,and hyperglycemia. An abdominal computerized tomography(CT) for investigating the cause of hypertension revealed an 87
mm solid mass located in the anterior part of the bladder. The
patient’s blood pressure was 232 / 129 mmHg, heart rate was 115
bpm and the initial hemoglobin A1c was 9.6%. Levels of serum
catecholamines, dehydroepiandrosterone and tumor markers,
such as carcinoembryonic antigen, α-fetoprotein, neuron-specificenolase and urinary metanephrine fractions were normal. Urinalysis showed no hematuria, and urine cytology was negative.
(123) I-metaiodobenzylguanidine scintigraphy showed no uptake. Therefore, the diagnosis was essential hypertension, type2 diabetes, and non-functioning tumor.
The tumor was a circumscribed round mass, heterogeneously
enhanced in the late phase on contrast-enhanced CT (CECT).
There was a poorly enhanced area on the left side of the tumor(Figure 1A). Continuity between the right lateral wall of thebladder and the tumor was suspected, but not definitively determined (Figure 1A). Magnetic resonance imaging (MRI)
T1-weighted images (T1WI) showed that the right side of thetumor had low-intensity areas like muscle tissue and the left sideof the tumor had a heterogeneous moderate-intensity area (Figure 1B). On MRI T2-weighted images (T2WI), the tumor wasclearly demarcated from the surrounding tissue, and the rightside of the tumor had remarkably low-intensity areas comparable to muscle tissue (Figure 1C). The left side of the tumor contained mixed low- and high-intensity areas (Figure 1D). T2WI
also showed suspected continuity, albeit slightly indistinct, between the tumor and the right lateral bladder wall (Figure 1C).
Since a primary retroperitoneal sarcoma could not be ruled
out, a laparotomy with tumor resection using a lower abdominal
Received for publication May 16, 2023 ; accepted July 31, 2023.
Address correspondence and reprint requests to Mami Taniuchi,
Department of Urology, Nippon Medical School Hospital, 1-1-5Sendagi, Bunkyo, Tokyo, Japan and Fax : +81-3-5685-1794.
E-mail : m-taniuchi@nms.ac.jp

midline incision was performed. The tumor was well demarcatedfrom the surrounding tissue and could be bluntly dissected. Post
dissection, a firm cord-like tissue from the right lateral wall ofthe bladder to the tumor was observed. Intraoperatively, thetumor was suggested to be benign based on demarcated margins
with a clear capsule, no tumor invasion into the surrounding
tissues, and well-defined morphology. The bladder was intact, except for the cord-like tissue contiguous with the tumor. A partial
cystectomy of approximately 10 mm square was performed withresection of the cord-like tissue and tumor. The operative timewas 71 min, and 10 ml blood was lost. The specimen weighed

Figure 1. Findings of the tumor on computerized tomography(CT) and magnetic resonance imaging (MRI). White arrows indicatetumors. White arrowheads show continuity between the tumor andthe bladder.
A. coronal late phase of contrast-enhanced CTB. axial T1 weighted image of MRI
C. sagittal T2 weighted image of MRI
D. axial T2 weighted image of MRI

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M. Taniuchi, et al. Primary leiomyoma of the bladder

112 g. The cord-like object was contiguous to the tumor (Figure2A, B). The cut surface was light brown, and some areas were
nodular and yellow in color (Figure 2B).

Figure 2. Specimen of the tumor

Black arrows show the cord between the tumor and the bladder.
A. Outside the tumor
B. Inside the tumor

Histopathological examination revealed a well-demarcated(Figure 3A), solid tumor with bundles of spindle-shaped cells
and an eosinophilic cytoplasm intersecting in a stereotypicalmanner. Overall, no nuclear atypia and mitotic figures wereobserved (Figure 3B). The tumor was positive for alpha-smoothmuscle actin (Figure 3C). The left side of the tumor exhibitededematous and hyaline degeneration. Microscopically, histologyof the cord-like object was identified as the bladder muscularis
propria (Figure 3D). Based on these findings, the tumor waspathologically diagnosed as a primary leiomyoma of the bladder.
One year after surgery, no recurrence was observed.

DISCUSSION
Bladder leiomyoma is a rare disease, accounting for approximately 0.43% of all bladder tumors (1). Primary bladderleiomyomas are classified into intravesical, intramural, andextravesical, with the last accounting for 30% (2). In all threetypes, bladder leiomyomas are typically continuous with thebladder broadly. This is the first report of an extravesical pedunculated bladder leiomyoma with poor continuity with the bladderthat was difficult to diagnose preoperatively.
CT and MRI are generally useful in the diagnosis of bladderleiomyoma ; on CT, a round-like, hypodense mass with a circumscribed margin was observed (3, 4). On CECT, tumors show
variable enhancement patterns upon contrast enhancement(4). Smooth-margined, low-signal tumors are typical on MRI,
characterized by moderate signal on T1W1 and low signals onT2WI (3-5). Furthermore, bladder leiomyomas typically involve
extensive lesions in the bladder (3-5). However, in the present
case, there was poor continuity between the bladder and thetumor, which is atypical for bladder leiomyoma (Figure 1C).
Therefore, performing preoperative imaging was challenging.
A retrospective review of the preoperative images revealed thatthe cord-like object had the same intensity as the bladder muscle
layer on MRI T2WI. The cord-like object was pathologically themuscularis propria of the bladder (Figure 3D). Therefore, it ispossible that the tumor originated from the outermost layer ofthe muscularis propria of the bladder and grew outward, resulting in a pedunculated tumor.
Laparotomy was selected based on the possibility that tumor
resection with wide margins might be required. Intraoperatively, the tumor was diagnosed as a primary benign bladder tumor
and a resection with minimal partial cystectomy was performed.
The standard treatment for bladder leiomyomas is transurethralresection or partial cystectomy, depending on the tumor location and size. Recently, several cases of benign bladder tumors
treated with laparoscopic or robot-assisted laparoscopic partial
cystectomy have been reported (6-8). In the present case, laparoscopic surgery would have been the treatment option if bladderleiomyoma had been preoperatively diagnosed.
In conclusion, preoperative imaging findings of continuity
between the bladder and tumor are useful for the diagnosis ofbladder leiomyoma.

CONFLICT OF INTEREST
The authors declare no conflict of interest.

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Figure 3. Pathological findings of the tumor

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C. Original magnification, ×100 ; α-SMA ×100. The tumor wasα-SMA positive.
D. Original magnification, ×100 ; hematoxylin and eosin staining.
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