Pathologists are likely to encounter IgG4-related disease in several organ systems. This article focuses on helping pathologists diagnose IgG4-related disease in the hepatobiliary system. Missing the diagnosis can result in unnecessary organ damage and/or unnecessary surgical and cancer therapy. In the liver, tumefactive lesion(s) involving the bile ducts with storiform fibrosis and an IgG4-enriched lymphoplasmacytic infiltrate are highly concerning for IgG4-related disease. The recent identification of oligoclonal populations of T cells and B cells in IgG4-related disease may lead to molecular tests, new therapeutics, and a greater mechanistic understanding of the disease.
Key points
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IgG4-related disease (IgG4-RD) can present in the liver as cholangitis with or without tumefactive lesions. IgG4-RD affects a wide range of ages and both genders, but most commonly middle-aged to elderly men.
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Although imperfect, histology currently represents the single best gold standard for diagnosis of IgG4-RD. Classic histologic appearance is storiform fibrosis, obliterative phlebitis, and an IgG4-enriched lymphoplasmacytic infiltrate.
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An enriched IgG4 + lymphoplasmacytic infiltrate (IgG4:IgG ratio >0.4) supports, but is not sufficient for, a diagnosis. An interdisciplinary approach integrating pathologic features, imaging, and clinical history is necessary for diagnosis.
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IgG4-related sclerosing cholangitis (IgG4-SC) is an uncommon disease and a wide differential diagnosis should be considered, one that includes primary sclerosing cholangitis (PSC), bile duct carcinoma, intrahepatic cholangiocarcinoma, inflammatory myofibroblastic tumor (IMT), and lymphoproliferative disorders.
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Recent evidence suggests that IgG4-RD is associated with unique T-cell and B-cell oligoclonal populations that may help with diagnosis of IgG4-RD and uncover unique therapeutic targets.
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