Urinary bladder mass in a three-month-old boy: Rhabdomyosarcoma (botryoid sarcoma)

A three-month-old boy presented with increasing difficulty with micturition for two weeks without haematuria, pain or palpable abdominal mass.
Urine examination showed plenty of red blood cells. Culture was sterile.

Ultrasound showed a solid lobulated mass arising from the bladder neck.
Cystourethrography revealed a lobulated filling defect at the bladder base.
MRI confirmed the mass, hyperintense on T2-weighted images. Perivesical fat planes were maintained.
Metastatic work-up was negative.
The patient was treated with surgery, chemotherapy and radiotherapy.

Rhabdomyosarcomas of the genitourinary tract are uncommon tumours nearly exclusive to the paediatric population and the most common malignant pelvic tumour in the young child.
Bladder and prostatic primaries account for 50% of genitourinary sarcomas. Rhabdomyosarcoma typically arises from the prostate or the trigone of the bladder in boys, and from the vagina or uterus in girls. [1]
The peak incidence of tumours is between 3-6 years of age with a 2-3/1 male predominance. Paratesticular tumours are the only genitourinary tract rhabdomyosarcomas that tend to occur in older children, typically adolescents. [2]
Bladder rhabdomyosarcomas commonly affect the posterior wall and show preference for the bladder neck and trigone. [3]

There are four major subtypes: embryonal, botryoid, alveolar and undifferentiated.
Bladder/prostate rhabdomyosarcoma is typically either embryonal or botryoid.
The embryonal cell type represents more than half of all histological subtypes.
Botryoid rhabdomyosarcoma is a variant of embryonal type and the most frequent to affect the bladder.
This tumour is frequent in mucosa-lined hollow visceral organs like vagina or urinary bladder, does not penetrate the overlying epithelium and shows intraluminal polypoid growth. Macroscopically the mass is composed of smooth, grapelike clusters of multiple, soft, polypoid gray nodules with translucent and gelatinous appearance. [4]
Microscopically it has a myxoid histologic pattern and a characteristic submucosal zone of increased cellularity referred to as the “cambium layer”. [4]

Patients usually present with urinary symptoms (haematuria, dysuria and urinary retention with distended bladder). Metastases occur most frequently in lymph nodes, lungs and cortical bones but also in liver and bone marrow. [4]

Ultrasonography is the first imaging investigation and typically shows a polypoid intraluminal mass with variable solid and cystic elements and variable internal flow.
Cystography typically shows a lobulated filling defect in relationship with the bladder wall. Small tumours that are better seen during the early filling may be obscured as more contrast material enters the bladder.

MRI helps to delineate the mass, typically hyperintense in T2-weighted images due to its myxoid histologic pattern.
CT is used to detect distant metastases.

The prognosis of localised tumours is good. [5] Appropriate treatment combines chemoradiotherapy and surgery. The indications of conservative and radical surgery remain controversial [6].
Although the chance of recurrence is greater in the first two years, patients should be followed up over an extended period of time as delayed recurrence has been reported.

Written informed patient consent for publication has been obtained.