Teaching Case

Male, 16 years old, previously healthy.  Presents to ER with hematuria, dysuria, and urinary urgency since the previous day and asthenia for 3days. Besides striking hematuria, clinical and laboratory examinations are unnoteworthy. A bladder ultrasound is performed, uncovering a 10cm bladder mass.

The ER ultrasound revealed a 10cm heterogeneous mass, abutting the anterior bladder wall, with intra and extraluminal extension and positive Doppler signal. (Fig. 1)

At MRI the mass was T2 hyperintense, T1 hipo-isointense, had slightly heterogenous contrast uptake and no restriction on ADC. The intravesical component was enveloped by a thick, T2 hypointense material, probably hemorrhagic. (Fig. 2)

At CT the density was slightly heterogeneous (predominantly low). The intraluminal component of the neoplasm was surrounded by a high-density material, likely hemorrhagic. (Fig. 3)

A partial cystectomy was performed. An inflammatory myofibroblast tumor with myxoid stroma was diagnosed at pathology. The patient has had no recurrence after a 7-year follow-up.

Inflammatory myofibroblastic tumor (IMT) is a rare tumor composed of myofibroblastic and fibroblastic spindle cells in associating with an inflammatory cell infiltrate. [1; 2]

IMTs occur anywhere in the body, most frequently in the lungs and abdominal cavity of children and young adults. Nevertheless, a wide anatomic distribution and a broad age range have been documented. [1] IMTs are infrequent in the genitourinary system and more commonly involve the urinary bladder, [2] 25% of all bladder IMTs manifest in children. [3]

Urinary Bladder IMTs most frequently present as macroscopic hematuria. Other presenting symptoms as pollakiuria, dysuria, abdominal/pelvic pain or obstruction symptoms have also been reported. [2]

The pathological mechanism of IMT is not fully understood, but it is though that an abnormal response to long-standing exogenous stimuli (virus, surgery, autoimmune aetiology, etc.) may induce tumorigenesis. [4]. Around 50–60% express ALK, which have a better prognosis. [4]  Histologically there are mainly three patterns: nodular fasciitis-like (myxoid/hyaline stroma), hypercellular (compact), and hypocellular (sclerotic, scar-like). [2]

IMTs imaging features are not specific. Tumours may appear in any area of bladder, commonly in the superior/anterior wall. [5] Bladder IMTs are described as nodules or masses that may extend into the lumen or submucosal area with/without fatty infiltration.[6] Ultrasonography is usually the first-line imaging modality. Bladder IMTs CT attenuation ranges from low to high density. [6] On MRI, these lesions may show hypo-to-isointense signal on T1 and hypo-to-hyperintense signal or mixed signal on T2. [6] The varying histology influences MRI signal: hypointense T1 and T2 lesions may reflect a fibrotic nature and lesions with higher cellularity or myxoid stroma component have more hyperintense T2 signal. [7] Tumours may show ring or significantly heterogeneous enhancement. [5] The fibrotic component exhibits persistent and delayed contrast uptake. [1; 8]

IMTs have a good prognosis and are considered of intermediate biologic potential, rarely metastasizing (<5%). [8] Due to the risk of local recurrence (25%), complete resection is recommended. After resection, no adjuvant therapy is currently indicated. Systemic treatments are reserved for advanced, non-operable disease. [1] Imaging is relevant for IMTs diagnosis and follow-up, providing an estimation of the size and involvement of the bladder wall.  Because bladder IMTs can have an appearance similar to bladder malignant tumors as rhabdomyosarcomas, a definitive diagnosis requires tissue biopsy. [3]