Teaching Case

64-years old male patient presented to the emergency room with macrohematuria, dysuria and fever. On physical examination, lower abdomen palpation felt uncomfortable but not painful. The patient had the history of hypertension but no history of using antiagregants or anticoagulants.
No history of trauma. The blood tests revealed slightly elevated inflammation and renal function markers: WBC 10,34, CRP 40 and creatinine 109. The urinalysis showed positive result for red blood cells, white blood cells, protein, nitrites.

Ultrasound in the emergency department described blood clots and bladder wall thickening. The patient had been catheterized before the ultrasound, so the bladder was almost empty during the procedure and evaluation was hence more complicated. The decision for further imaging was made due to the significant macrohematuria and as the clinical picture was untypical of just being caused by cystitis. CT of the abdomen and pelvis revealed a well-defined homogenous tumour 8,1 x 7,2 x 6,8cm in the lower bladder wall that enhanced minimally (~10HU difference between non-CE and CE images). The bladder wall in the upper area was thicker and showed signs of inflammation. MRI revealed a well-defined, T2 low-intensity tumour 8,5cm that had low/moderate contrast enhancement and diffusion restriction.

Background

Leiomyoma of the bladder is the most common mesenchymal tumour of the bladder but accounts only for <0,5% of all bladder tumours. Histologically, leiomyomas are non-infiltrative benign smooth muscle tumours lacking mitotic activity, cellular atypia, and necrosis. [1] The aetiology of these benign tumours is relatively unknown. It has been speculated that bladder leiomyomas might arise from either chromosomal alterations, hormonal disturbances, repeated bladder wall and detrusor infection, perivascular inflammation or dysontogenesis. Leiomyomas are classified into three different locations, i.e. endovesical, intramural and extravesical. Endovesical is the most common location and it corresponds to 63–86% of cases, while extravesical are seen in 11–30% and intramural leiomyomas in 3–7% cases. [2]

Clinical Perspective

Bladder leiomyomas have been shown to have a similar incidence among both sexes. Approximately 75% of the patients are young and middle-aged [3]. Smaller tumours can be asymptomatic and are thus found as incidentalomas. Majority of the patients present with voiding problems: obstructive symptoms (49%), irritative symptoms (38%) and haematuria (11%) [1,2] Lower urinary tract complaints are common and the 1
differential diagnosis list of all these symptoms is long, starting with simple infections, prostate-related diseases as well as bladder tumours.

Imaging Perspective

Bladder leiomyomas exhibit characteristics similar to those of their uterine counterpart at US, CT, and MR imaging, with MR imaging being most specific for tissue characterization. Typically, leiomyomas exhibit intermediate signal intensity on T1-weighted images and low signal intensity on T2-weighted images. Degenerated leiomyomas have more heterogeneous signal characteristics, with cystic areas having high signal intensity on T2-weighted images. Contrast enhancement is variable, with degenerated areas lacking enhancement.[1]

Outcome

Surgical removal is the treatment of choice, but the resection volume depends on the localisation and size of the tumour. Small and accessible tumours can be treated with transurethral resection of the bladder tumour, tumours with unfavourable positioning may require segmental resection, partial cystectomy or cystoprostatectomy [2]

Take Home Message / Teaching Points

Leiomyomas of the bladder, although being the most frequent mesenchymal tumours of the bladder, are rare. A preoperative suspicion of a leiomyoma is invaluable information and thus alerting the surgeon of the benign nature of the mass can prevent unnecessary radical surgery. Although there are certain characteristics ( bigger size, non-enhancing areas in the tumour caused by necrosis) that help to differentiate leiomyoma from leiomyosarcoma in the bladder, it is not final. Differentiation of a well-differentiated leiomyosarcoma from leiomyoma by diagnostic imaging is difficult and the final evaluation needs to be done histologically.

Final diagnosis was established after cystoprostatectomia. Pathology revealed a bladder wall intramural mass 8,5 x 8,0 x 7,5cm that origined from the muscular layer, which had positive myogenic markers (SMA, DES, Caldesmon and Calponin), no malignant cells were present. Histology confirmed the diagnosis of leiomyoma.