Inflammatory myofibroblastic tumor versus igg4-related sclerosing disease and inflammatory pseudotumor: A comparative clinicopathologic study

Hidetaka Yamamoto, Hiroshi Yamaguchi, Shinichi Aishima, Yoshinao Oda, Kenichi Kohashi, Yumi Oshiro, Masazumi Tsuneyoshi

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131 Citations (Scopus)


Inflammatory pseudotumor (IPT) is a heterogeneous group of lesions occurring in various organs, which is histologically characterized by fibroblastic and myofibroblastic proliferation with inflammatory infiltrate. Inflammatory myofibroblastic tumor (IMT) is a neoplastic counterpart of IPT, which shows aberrant expression of ALK and its gene translocation. In contrast, the concept "immunoglobulin (Ig)G4-related IPT" in the lung, liver, and pancreas has recently been proposed as a member of IgG4-related sclerosing disease. In this study, we compared the histopathologic features with an emphasis on IgG4 expression between 22 cases of IMT and 16 cases of IgG4-related sclerosing disease, including chronic sclerosing sialadenitis (n=8), mass-forming autoimmune pancreatitis (n=3), sclerosing cholangitis (n=1), retroperitoneal fibrosis (n=2), and chronic sclerosing dacryoadenitis (n=2). Bland-looking spindle cell proliferation with fibrosis and inflammatory infiltrate of lymphocytes and plasma cells was the common morphologic feature in both lesions. Obstructive phlebitis was observed in all of the IgG4-related sclerosing lesions, but in only 1/22 (4.5%) of IMT. The immunohistochemical expression of ALK was observed in 15/22 (68.2%) of IMT and 0/16 (0%) of IgG4-related sclerosing disease. The number of IgG4-positive plasma cells and the ratio of IgG4+/IgG+ plasma cells were each significantly lower in IMT than in IgG4-related sclerosing disease [mean 6.4/HPF vs. 178.3/HPF (P<0.0001), 3.0% vs. 67.5% (P<0.0001), respectively]. The results suggest that IgG4 does not play an important role in the pathogenesis of IMT. In addition, the evaluation of IgG4+ plasma cells and the ratio of IgG4+/IgG+ plasma cells and the presence of obstructive phlebitis may be useful for the differential diagnosis between IMT and IgG4-related sclerosing disease.

Original languageEnglish
Pages (from-to)1330-1340
Number of pages11
JournalAmerican Journal of Surgical Pathology
Issue number9
Publication statusPublished - Sep 1 2009


All Science Journal Classification (ASJC) codes

  • Anatomy
  • Surgery
  • Pathology and Forensic Medicine

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