Case: AP247
Contributor's Comment: Inflammatory pseudotumour is defined as a benign, non-neoplastic, non-metastasizing mass composed of fibrous tissue and proliferated myofibroblasts, with a marked inflammatory infiltration. The etiology of this lesion remains largely unknown, although the myofibroblastic nature of the spindle cells has been well established. In the liver, most probably it is a heterogenous lesion, with various infectious and inflammatory causes being proposed. Lately, IgG4-related disease turns out to be an important subgroup, which features a fibroblastic mass with marked lymphoplasmacytic infiltration, many eosinophils, numerous IgG4-positive plasma cells, dense fibrosis of hilar and extrahepatic bile ducts and obliterative phlebitis, and showing response to steroid therapy. The spectrum of hepatic IgG4-related diseases ranges from sclerosing cholangitis (affecting intra- and/or extra-hepatic bile ducts) to mass forming lesion as in the present case. (MST)
Reference: Zen Y, Harada K, Sasaki M, Sato Y, Tsuneyama K, Haratake J et al. IgG4-related sclerosing cholangitis with and without hepatic inflammatory pseudotumor, and sclerosing pancreatitis-associated sclerosing cholangitis: do they belong to a spectrum of sclerosing pancreatitis? Am J Surg Pathol 2004;28:1193–1203.