Inflammatory Myofibroblastic Tumor of the Urinary Bladder Presenting as a Radiological cT3 Mass: A Case Report and Narrative Review of 89 Cases.

BACKGROUND/AIM: Inflammatory myofibroblastic tumor (IMT) of the urinary bladder is a rare mesenchymal neoplasm of intermediate malignancy that frequently mimics locally advanced urothelial carcinoma on imaging. The optimal surgical management when computed tomography suggests extravesical invasion remains undefined. CASE REPORT: A 57-year-old man presented with persistent dysuria without gross hematuria. Computed tomography demonstrated a heterogeneously enhancing anterior bladder wall tumor (30×29 mm), with perivesical fat stranding, radiologically staged as cT3N0M0. Transurethral resection of the bladder tumor (TURBT) was performed as the index procedure. Histopathology revealed spindle-cell proliferation in a myxoid stroma with mixed inflammatory infiltrate. Immunohistochemistry confirmed diffuse, moderate-to-strong cytoplasmic positivity for anaplastic lymphoma kinase (ALK) using the D5F3 clone; staining for proto-oncogene tyrosine-protein kinase (ROS) was negative. A diagnosis of IMT of the urinary bladder was established. Serial cystoscopy at 3, 6, 9, 12, and 18 months showed no intravesical recurrence. Computed tomography at 6 months demonstrated stable residual perivesical soft tissue, without progression. The patient remained recurrence-free at 51 months post-TURBT with his bladder intact. CONCLUSION: Bladder IMT can radiologically simulate locally advanced urothelial carcinoma including apparent extravesical invasion. TURBT should precede any irreversible surgical decision, as pathology rather than staging by computed tomography determines the correct operation. ALK immunohistochemistry is mandatory in the workup of all non-urothelial spindle-cell bladder tumors.