title: IgG4-related kidney disease from the renal pelvis that mimicked urothelial carcinoma: a case report.
abstract: BACKGROUND
  IgG4-related kidney disease is a comprehensive term for renal lesions associated with IgG4-related disease, which mainly manifests as plasma cell-rich tubulointerstitial nephritis with increased IgG4+ plasma cells and fibrosis. IgG4-related kidney disease in the renal pelvis is rare.
  
  
  METHODS
  We describe a 53-year-old Asian woman who was referred to our hospital with a space-occupying renal lesion discovered by medical examination. A physical examination and laboratory evaluation revealed no significant abnormalities. Computed tomography scans showed a soft-tissue mass with an irregular border and mild homogeneous enhancement in the right renal pelvis and calyces. A positron emission tomography/computed tomography scan revealed soft-tissue density shadows with increased radionuclide uptake. To investigate a suspected pelvic carcinoma, a right ureteronephrectomy was performed. A pathologic examination of the renal sections showed a dense lymphoplasmacytic infiltrate rich in IgG4+ plasma cells, with fibrosis beneath the urothelial epithelium of the renal pelvis. Postoperatively, the serum IgG4 level was significantly elevated. The patient was diagnosed with IgG4-related kidney disease.
  
  
  CONCLUSIONS
  We present a case of IgG4-related kidney disease mimicking urothelial carcinoma in the renal pelvis. When a buried and solitary hypovascular tumor is detected in the kidney, we must consider IgG4-related kidney disease as a differential diagnosis. Accordingly, elevated serum IgG4, radiologic findings, and pathologic examination may improve the diagnosis.
authors.affiliation: Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Shuaifu Yuan, Beijing, 100730, PR China. moshanghuizi@126.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Shuaifu Yuan, Beijing, 100730, PR China. renxinyu7956@163.com.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Ren
authors.affiliation: Department of Rheumatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100730, PR China. lovemexiehe@126.com.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Shuaifu Yuan, Beijing, 100730, PR China. pumchzhanghui@126.com.
authors.forename: Di
authors.initials: D
authors.lastname: Yang
authors.affiliation: Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Shuaifu Yuan, Beijing, 100730, PR China. fengruie1@163.com.
authors.forename: Ruie
authors.initials: R
authors.lastname: Feng
mesh_terms: D001707:Biopsy, Needle; D002295:Carcinoma, Transitional Cell / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D007682:Kidney Pelvis / Q000000981:diagnostic imaging / Q000473:pathology*; D008875:Middle Aged; D009392:Nephrectomy / Q000379:methods; D009393:Nephritis / Q000175:diagnosis* / Q000276:immunology* / Q000601:surgery; D049268:Positron-Emission Tomography / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D007074:Immunoglobulin G