Idiopathic segmental ureteritis, misdiagnosed as ureteral cancer preoperatively: a case report with literature review.

A 53-year-old man presented with right flank pain for 6 days. Computerized tomography revealed a 3 cm long segment of ureteral narrowing with wall thickening and hydronephrosis, suspicious for ureteral cancer. Under the clinical diagnosis of ureteral carcinoma a right nephroureterectomy was performed. The wall of the distal ureter, 2.5 cm from the bladder cuff, had a luminal-narrowing, firm mass-forming lesion with abrupt transition from the adjacent ureter. Histologically, the resected ureteral mass showed transmural fibrosing, chronic inflammation with numerous plasma cells, epithelioid granulomas, and obliterative phlebitis. Histological findings were consistent with idiopathic segmental ureteritis (ISU) with differential diagnoses of IgG4-related sclerosing disease, including lymphoplasmacytic inflammatory pseudotumor (IPT) and idiopathic retroperitoneal fibrosis. IgG4 immunostaining in this case was barely positive, excluding the possibility of IgG4-related IPT. Although the majority of luminal obliterated segmental lesions of the ureter are neoplastic in nature, non-neoplastic inflammatory processes as seen in this case may occur in the ureter, causing diagnostic confusion with true neoplasms. Herein we report a rare case of ISU that was clinically misdiagnosed as malignancy preoperatively. ISU of the current case may be an IgG4-unrelated subtype of IPT.