IgG4-related disease of the ureter: report of two cases and review of the literature.

IgG4-related disease (IgG4-RD) is a recently recognized multi-organ fibro-inflammatory lesion characterized by elevated IgG4 serum levels and mass-forming lesions. This condition shows similar histological features independently of the site of origin including storiform fibrosis, obliterative phlebitis, and dense lymphoplasmacytic infiltrate with a conspicuous IgG4-positive plasma cell component. Since this disease has only recently been categorized as a single specific nosologic entity, lesions with these typical morphological features have previously been named in different ways, creating some confusion and making it difficult to identify cases published in the literature. Lesions with features suggesting IgG4-RDs have very rarely been reported in the ureter, and they have been named using the terms "inflammatory pseudotumor" and "idiopathic segmental ureteritis." Herein, we describe the clinicopathological features of ureteral IgG4-RD found in two different patients. An 82-year-old female and a 77-year-old male underwent ureteral resection due to severe ureteral wall thickness and lumen stenosis suggestive of urothelial carcinoma. However, histological examinations showed transmural fibro-inflammatory lesions, with abundant IgG4 plasma cells intermixed with histiocytes, lymphocytes, fibroblasts, and scattered eosinophils. We have also accurately reviewed the literature in order to identify, among lesions diagnosed with different names, examples of ureteral IgG4-related lesions to give the reader a comprehensive overview of this relatively rare inflammatory disease. We suggest using the name "ureteral IgG4-RD" for those lesions showing the same morphological features as IgG4-RDs located elsewhere.