[Inflammatory myofibroblastic tumor of the renal pelvis].

Inflammatory myofibroblastic tumor (IMT) of the genitourinary tract is rare and has been classified into separate groups based on their anatomical site and postulated aetiology. Herein, we present a case of IMT of the renal pelvis. A 44-year-old man presented with gross hematuria. Abdominal computed tomography (CT) and magnetic resonance imaging (MRI) revealed a tumor of the left renal pelvis. Under the diagnosis of left renal pelvic tumor, he underwent left nephrectomy and ureterectomy. Microscopic examination revealed fascicular spindle cell proliferation in an oedematous myxoid background with an infiltrate of plasma cells. The spindle cells were strongly positive for smooth muscle actin (SMA) and vimentin, and negative for desmin and anaplastic lymphoma kinase (ALK). Diagnosis of the lesion was IMT of the renal pelvis.