[851] Xanthogranulomatous Pyelonephritis (XGP) of Kidney: Another IgG4 Associated Pseudotumor?

Sung Hee Kang, Sun A Kim, Seongmuk Jung, Yong Mee Cho, Alberto G Ayala, Jae Yoon Ro. Universitiy of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea; Pusan University Hospital, Pusan, Korea; Weill Medical College of Cornell University, The Methodist Hospital, Houston

Background: XGP is an uncommon chronic inflammatory disorder with uncertain histogenesis. During routine sign out, a case of XGP showed significant plasma cell infiltration (≥50 plasma cells/1hpf) with sclerotic inflammation and a subsequent IgG4 staining demonstrated numerous IgG4 positive plasma cells. This case prompted us to study the relationship between XGP and IgG4 associated sclerotic disease.
Design: We retrieved 15 cases diagnosed as XGP from the Surgical Pathology file of Asan Medical Center, Seoul, Korea from 1999 to 2010. Histologically an attempt was made to separate areas with predominance of inflammatory components (neutrophils, foamy histiocytes, lymphocytes, plasma cells) from areas predominantly depicting the sclerotic component. Immunohistochemical studies for IgG4 and IgG were performed. The number of IgG4 positive plasma cells was counted on 1 high power field and IgG4/IgG ratio was evaluated in both inflammatory component and sclerotic areas separately.
Results: Of the 15 patients with XGP, 13 were women and 2 were men. Their mean age was 55.8 years with a range of 34 to 74 years. All cases showed a mass forming lesion with clinical diagnosis of RCC. The lesions averaged in size 3.9 cm with a range of 1.5 cm to 13cm. Overall all cases showed numerous plasma cells and sclerotic reaction. The inflammatory component was significantly more abundant in the central areas than in the periphery of the XGP (P<0.001), while the sclerotic component was the reverse (P<0.001). Neutrophils and foamy histiocytes were more frequently observed in the center of the lesion (P=0.002, <0.001), but the distribution of lymphocytes and total plasma cells were not different between the center and the periphery of the lesions. However, the number of IgG4-positive plasma cells and IgG4/IgG ratio were significantly higher in the peripheral sclerotic areas compared to the central area (P=0.001, <0.001, respectively).
Conclusions: Based on our study, 1) not all but most of XGP seem to be related to IgG4 associated sclerotic disease. 2) The peripheral distribution of IgG4 positive plasma cells suggests that IgG4 positive plasma cells have an active role for a sclerotic phase of the disease. Lastly 3) to establish XGP being another IgG4 positive pseudotumor, more studies are required for the histogenesis and potential treatment.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 138, Wednesday Afternoon


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