PMC5933309_01
Axial T2-weighted magnetic resonance imaging (MRI) of the pelvis showing the amount of soft tissue before (A) and after (B) therapy. A: There is increased soft tissue in the retroperitoneum inferior to the aortic bifurcation, the cause of the bilateral ureteral obstruction. B: The amount of soft tissue in the retroperitoneum distal to the aortic bifurcation has markedly decreased. There is mild reduction in the right hydronephrosis and significant reduction in the left hydronephrosis. White arrows point to areas of retroperitoneal fibrosis.
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Figure1
It also demonstrated nonspecific presacral and retroperitoneal fat stranding (Figure 1). A retrograde pyelogram revealed diffuse mucosal irregularity of the right ureter (Figure 1). To further investigate the CT scan finding, an MRI of the abdomen and pelvis was performed, demonstrating increased soft tissue in the retroperitoneum inferior to the aortic bifurcation, which was thought to be the cause of her ureteral obstruction (Figure 1).
Retroperitoneal biopsy findings. A: Hematoxylin and eosin staining showing fibrous proliferation with hyalinized collagen, focally-forming storiform fascicles, dense lymphoplasmacytic infiltrate (yellow arrowhead) with occasional germinal centers. Black arrowheads showing the normal retroperitoneal fibro-adipose tissue. B: High-power field showing classical plasma cell (white arrowhead) within the infiltrate; immunohistochemical staining assessment of the IgG4/IgG ratio performed by quantification of stained cells, showing IgG-positive lymphocytes and plasma cells of 60 - 70/high-power field (C), and IgG4-positive lymphocytes and plasma cells of 30/high-power field (D), demonstrating an IgG4/IgG ratio of 42 - 50%.
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Figure2
During the procedure, the retroperitoneal soft tissue density was biopsied, which revealed fibrous proliferation with hyalinized collagen, focally-forming storiform fascicles, dense lymphoplasmacytic infiltrate with occasional germinal centers (Figure 2A, B), and focal obliterative phlebitis. Immunohistochemical staining revealed IgG4-positive plasma cells (60 - 70/high-power field), and the IgG4/IgG plasma cell ratio was > 40% (Figure 2C, D), in support of a diagnosis of IgG4-RD.