ABSTRACT
Background: Immunoglobulin G4-related disease (IgG4-RD) is an immune mediated fibro inflammatory condition characterized by abundant IgG4-positive (IgG4+) plasma cell infiltrated lesions and elevated serum IgG4 concentrations. Tubulointerstitial nephritis and glomerular lesions are the most common renal IgG4-RDs. However, solitary mass lesion is rarely observed in renal IgG4-RD. Materials and Methods: We reported a 55-year-old male patient with a space-occupying lesion in the right kidney detected during a routine ultrasound medical examination. Computed tomography indicated a 20 mm × 15 mm × 18 mm mass located at the lower pole of the right kidney. Both T1-weighted imaging and T2-weighted imaging magnetic resonance imaging scans showed a hypointense mass. Diffusion-weighted imaging (b value = 800) showed slightly hyperintensity. Results: The lesion was diagnosed as renal cell carcinoma clinically based on the laboratory and radiological findings and treated with laparoscopic resection. However, the postoperative histological examination results indicated the lesion IgG4-RD of the kidney. Conclusion: We should consider pseudotumor-like IgG4-RD as a differential diagnosis for solitary renal lesion although the incidence is low