Teaching Case

A 78-year-old female patient presented with urinary infection symptoms. On an outpatient clinic a pelvic ultrasound was performed detecting a tumour in the anterior bladder wall. The patient initially was evaluated with computed tomography (CT) followed by cystoscopy. This tumour was resected with open partial cystectomy.

On pelvic CT a well-defined heterogeneous solid lesion was seen in the anterior bladder wall, with a biconvex shape (Fig. 1. a, b, d and e), regular contour and progressive enhancement (Fig. 1). This lesion was surrounded interiorly by a regular line, which continued with the bladder wall (Fig. 1a, 1b and 1d). These findings were suggestive of an intramural bladder wall tumour.
On cystoscopy a solid lesion was detected in the anterior bladder wall, protruding to the bladder lumen, with preserved covering mucosa (Fig. 2a). This tumour was not related to the uterus (Fig. 2b) and the ureteral meatus were unaffected (Fig. 2c).
Macroscopic surgical specimen of partial cystectomy described a well-defined encapsulated solid tumour, surrounded by bladder wall muscle with no smooth muscle infiltration, limited interiorly by mucosa (arrowhead) and externally by serosa (arrow) (Fig. 3), constituted by fascicles of smooth muscle fibres separated by connective tissue.

Bladder leiomyomas (BLM) are extremely rare urinary tumours accounting for less than 0.5% of all bladder tumours. [1, 2] However, BLM are the most common benign mesenchymal bladder neoplasms. [1, 2] BLM ethology is indeterminate. [1, 2, 3]

BLM are more frequent in women (70%), and more common from third to sixth decade of life. [1, 2] BLM are classified as: intravesical (63%-86%), extravesical (11%-30%), and intramural (3-7%). [3, 4, 5] Their presentations vary with their location and size. In most cases BLM present with obstructive (49%) and irritative (38%) symptoms, both more common in intravesical forms, and haematuria (11%). They can also be asymptomatic, commonly in intramural and extravesical BLM, delaying their diagnosis. [3, 4, 5]

Imaging examinations are important in BLM detection and evaluation. The majority of imaging techniques shows features suggestive of the benign nature of BLM, like well-circumscribed lesions with intact mucosal layer and normal perivesical fat. [3, 4] On ultrasound BLM usually appear as homogeneous smooth-walled lesions, with internal echoes, and peripheral hyperechogenicity. [1, 2, 4] On CT BLM appear as smooth-walled bladder mass with attenuation coefficient ranging from 25 to 50 HU, with no involvement of bladder adjacent structures. [2, 4, 6]
MRI is the most specific imaging technique for BLM diagnosis. Typically BLM show intermediate signal intensity on T1-weighted sequences and hypointensity on T2-weighted sequences, similar to uterine leiomyomas. When degenerated, BLM are heterogeneous, with cystic areas that appear hyperintense on T2-weighted sequences and calcifications hypointense on T1- and T2-weighted sequences. [5, 7, 8] After intravenous contrast administration, BLM may range from homogeneous to heterogeneous enhancement patterns, depending on their components. [5, 7, 8]
Cystoscopy is extremely helpful in bladder lesions characterization, enabling their biopsy and diagnosis in the majority of the cases, and sometimes treatment. On cystoscopy BLM typically appear as a smooth bladder mass with preserved covering mucosa. [2, 3, 7]

BLM diagnosis is confirmed by histopathologic analysis, excluding malignancy and guiding appropriate treatment. [2, 3, 6] This tumour shows similar histopathological features as uterine leiomyoma and it is identical to bladder wall muscle samples, with no infiltrative features. [1, 2, 4] This way is essential to know their exact location for tissue sampling. [5]

BLM treatment depends on their size and location, ranging from transurethral resection for small intravesical lesions to partial cystectomy. [3, 4, 5] Their wide excision prevent BLM recurrence. [1, 4, 6] Benign BLM lesions have a good outcome. [4, 5, 6]

BLM should be included in bladder wall lesions differential diagnosis, preventing unnecessary radical surgery of these benign neoplasms.