IgG4-related retroperitoneal fibrosis

Case contributed by Bruno Di Muzio


LIF and left flank pain.

Patient Data

Age: 60 years
Gender: Female

CT Abdomen and pelvis


There is an ill-defined heterogeneously enhancing mass-like lesion encasing the left common iliac vessels and ureter. It has a granular/multinodular appearance with some permeating stranding. As a consequence, there is mild upstream hydroureter and hydronephrosis. No lymphadenopathy elsewhere in the abdomen. The solid and hollow abdominal viscera are unremarkable. 


Nuclear medicine

The retroperitoneal lesion has strong FDG avidity. 

CT Abdomen and pelvis (post-operative)


The retroperitoneal lesion has been mostly removed surgically and a left ureteral stent has been placed. 

Macroscopy:  Labeled "Retroperitoneal mass".  A specimen measuring 72 x 51 x17 mm.  On sectioning tissue appears grey/yellow and gelatinous.  Inked black and green opposing sides. Sample kept fresh.

Frozen section diagnosis: Abnormal tissue, favor a reactive process.

Comment: The histological features of a dense lymphoplasmacytic infiltrate, fibrosis, and obliterative phlebitis, coupled with IgG4+ plasma cells exceeding an average of 60 per high power field is in keeping with the diagnostic category of 'histologically highly suggestive of IgG4-related disease' as recommended by the Boston Consensus Statement on the pathology of Ig4-related disease (Ref:  Modern Pathology 2012:25;1181-1192.)  However, the IgG4+: IgG+ ratio does not exceed 40% as would be expected for this diagnostic category.  IgG and IgG4 immunohistochemistry will be performed on a second block and the ratio re-examined, the result of which will follow in a supplementary report.  Correlation with clinical findings and serum IgG4 concentration required.

Opinion: Retroperitoneal mass:  Histologically highly suggestive of IgG4-related disease.

Additional immunohistochemistry has been performed.

Repeat IgG4:IgG plasma cell ratio has been performed on additional tissue blocks.  Within Block A2, three high power fields are identified within which the ratio exceeds 40%. Both kappa and lambda positive plasma cells are present.

ALK immunohistochemistry is negative.

The findings of the initial report remain unchanged.  However, it should be noted that the presence of multinucleated giant cells is not entirely characteristic of IgG4-sclerosing disease and giant cell arteritis may warrant exclusion.  Please correlate with clinical, radiological and serological findings.

Case Discussion

Retroperitoneal fibrosis represents a chronic inflammatory process related to many possible underlying causes, including IgG4-related disease. 

Lymphoma and large-vessel vasculitis should also be included in the differential diagnosis.

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