title: Inflammatory myofibroblastic tumor versus IgG4-related sclerosing disease and inflammatory pseudotumor: a comparative clinicopathologic study.
abstract: 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.
authors.affiliation: Department of Anatomic Pathology, Pathological Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. hidetaka@surgpath.med.kyushu-u.ac.jp
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Shinichi
authors.initials: S
authors.lastname: Aishima
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Oda
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kohashi
authors.forename: Yumi
authors.initials: Y
authors.lastname: Oshiro
authors.forename: Masazumi
authors.initials: M
authors.lastname: Tsuneyoshi
mesh_terms: D000328:Adult; D000368:Aged; D000077548:Anaplastic Lymphoma Kinase; D001327:Autoimmune Diseases / Q000276:immunology / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D015209:Cholangitis, Sclerosing / Q000276:immunology / Q000473:pathology; D002908:Chronic Disease; D003607:Dacryocystitis / Q000276:immunology / Q000473:pathology; D005260:Female; D006104:Granuloma, Plasma Cell / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D007223:Infant; D008297:Male; D008875:Middle Aged; D010195:Pancreatitis / Q000276:immunology / Q000473:pathology*; D010689:Phlebitis / Q000276:immunology / Q000473:pathology; D010950:Plasma Cells / Q000473:pathology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases; D012185:Retroperitoneal Fibrosis / Q000276:immunology / Q000473:pathology; D012598:Sclerosis; D012793:Sialadenitis / Q000276:immunology / Q000473:pathology*; D055815:Young Adult
chemical_list: D007074:Immunoglobulin G; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases