To summarize the characteristics of IgG4 related disease(IgG4-RD), and to avoid unnecessary surgical procedures due to misdiagnosis.

Retrospective analysis of the clinical data of one case of IgG4 related disease involving the renal pelvis in our hospital, and the clinical features of IgG4 related disease involving the renal pelvis were reviewed and discussed. A 56-year-old man presented with microscopic hematuria, CT showed right renal pelvis and ureteral wall thickening, local soft tissue density, post contrast CT showed low-density renal pelvic mass and the wall of the ureter-pelvic was irregularly thicken, indicating renal pelvic cancer and lymph node metastasis. PET-CT(18F-FDG) findings indicated that the renal pelvic mass was a malignant tumor, because the glucose metabolism was very high. The preoperative diagnosis was retroperitoneal lesion, suspecting renal pelvic carcinoma or lymphoma. The patient underwent 3D laparoscopic nephroureterectomy with out preoperative biopsy. During operation, we found extensive enlargement of the right renal portal and retroperitoneal lymph nodes, including that the renal portal and the renal pelvis mass had a serious adhesion to the vena cava and renal arterial vein.

Postoperative pathology results revealed lymphatic tissue hyperplasia and germinal center formation. Immunohistochemical staining showed that most plasma cells positive expression of IgG4 (IgG4>40%, IgG4>100 /HPF), reactive hyperplasia of lymph node, considering the IgG4 related diseases. Serum IgG4 level was 15.2 g/L(0.03-2.01 g/L)after operation. Combined with serological examination, IgG4 related disease was confirmed. There was no evidence of IgG4-related disease at any other site during the follow up period, thereby obviating the need for any additional therapy.

IgG4 related disease is a novel clinical disease entity characterized by elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells, which leads to the enlargement of the organ or nodular/proliferative lesions. The disease can be revealed as a soft tissue tumor of the renal pelvis and be misdiagnosed as malignant tumor. Surgical intervention could be avoided according to the correct diagnosis.

IgG4 related disease; Renal pelvic carcinoma; Surgery; Diagnosis and therapy