title: IgG4-related systemic disease mimicking renal pelvic cancer: a rare case.
abstract: BACKGROUND
  Immunoglobulin G4-related disease (IgG4-RD) is a new clinical entity. Characteristic features of IgG4-RD are elevated serum IgG4 levels, infiltration of IgG4-positive cells, mass-forming lesions with fibrosis and good response to corticosteroids. The variable imaging features of IgG4-RD and the overlap with other differential diagnoses often pose a diagnostic challenge, as they frequently mimic malignant tumors or other inflammatory diseases in the abdomen.
  
  
  METHODS
  A 54-year-old woman visited our hospital with left flank discomfort and palpebral edema. Computed tomography, magnetic resonance imaging, retrograde pyelography and positron emission tomography/computed tomography indicated renal pelvic cancer. However, after a left-sided nephroureteral cystectomy was performed, the mass was pathologically confirmed as an IgG4-related lesion. Her elevated serum IgG4 level and a past history of sicca complex supported the diagnosis of IgG4-RD.
  
  
  CONCLUSIONS
  It is critical to recognize the importance of laboratory examinations such as serum IgG4 level if a patient has a past history of rheumatic disease.
authors.forename: Yiwei
authors.initials: Y
authors.lastname: Wang
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.forename: Rongkui
authors.initials: R
authors.lastname: Luo
authors.forename: Hang
authors.initials: H
authors.lastname: Wang
authors.forename: Guomin
authors.initials: G
authors.lastname: Wang
authors.forename: Yingyong
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Department of Urology, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai 200032, China. guo.jianming@zs-hospital.sh.cn.
authors.forename: Jianming
authors.initials: J
authors.lastname: Guo
mesh_terms: D001327:Autoimmune Diseases / Q000097:blood / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007680:Kidney Neoplasms / Q000097:blood / Q000175:diagnosis*; D007682:Kidney Pelvis / Q000473:pathology*; D008875:Middle Aged; D010386:Pelvic Neoplasms / Q000097:blood / Q000175:diagnosis*; D049268:Positron-Emission Tomography; D011379:Prognosis; D014057:Tomography, X-Ray Computed
chemical_list: D007074:Immunoglobulin G