A huge recurrent retroperitoneal inflammatory myofibroblastic tumor implicating renal and ureter: a case report.

Inflammatory myofibroblastic tumor (IMT) is a rare sarcoma with unique molecular characteristics. It also has typical fasciitis-like, dense spindle cells and hypocellular fibrous histologic patterns and can occur at any age. The etiology of IMT is unknown and a complete treatment and monitoring plan for IMT have not been developed. We have found a rare case about a huge recurrent IMT implicating renal and ureter. The patient was accompanied by a history of a lesion sized 15.5 cm × 11.5 cm × 10.5 cm as a retroperitoneal IMT, and the first tumor resection was performed 12 months ago. The patient, who suffered from tumor recurrence within 1 year and whose recurrent tumor also invaded into the renal parenchymal was given a retroperitoneal neoplasm resection plus right nephrectomy. In order to clarify the pathological features, the histological specimens of recurrent retroperitoneal IMT were examined as well as primary retroperitoneal IMT, and immunohistochemical (IHC) stains showed that the spindle cells were positive for vimentin and negative for anaplastic lymphoma kinase (ALK). At 24 months follow-up, the patient recovered well and there was no evidence of tumor recurrence. This case report is conducive to understanding this rare tumor. When conditions permit, complete surgical resection is the recommended treatment for primary and recurrent IMT.