title: An inflammatory myofibroblastic tumor exhibiting immunoreactivity to KIT: a case report focusing on a diagnostic pitfall.
abstract: Inflammatory myofibroblastic tumors (IMTs) and gastrointestinal stromal tumors (GISTs) are both spindle cell tumors, and occur rarely in the wall of the urinary bladder. In general, immunostaining allows differentiation of IMTs and GISTs. Most IMTs are positive for anaplastic lymphoma kinase (ALK) and negative for KIT, whereas most GISTs are ALK-negative and KIT-positive. Here, we describe a case of a spindle cell tumor in the wall of the urinary bladder. The spindle cells were positive for both ALK and KIT, and it was thus difficult to determine whether the tumor was an IMT or a GIST. We eventually diagnosed an IMT, because ALK gene rearrangement was confirmed by fluorescent in-situ hybridization. Cytoplasmic staining for KIT and the absence of other GIST markers, including DOG1 and platelet-derived growth factor α, indicated that the tumor was not a GIST. Therefore, IMTs should be included in the differential diagnosis of spindle cell tumors, even those that are KIT-positive.
authors.forename: Tatsuki R
authors.initials: TR
authors.lastname: Kataoka
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Yamashita
authors.forename: Ayako
authors.initials: A
authors.lastname: Furuhata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hirata
authors.forename: Takaki
authors.initials: T
authors.lastname: Ishida
authors.forename: Ichiro
authors.initials: I
authors.lastname: Nakamura
authors.forename: Seiichi
authors.initials: S
authors.lastname: Hirota
authors.affiliation: Department of Diagnostic Pathology, Kyoto University Hospital, Sakyo-ku, Kyoto 606-8507, Japan. haga@kuhp.kyoto-u.ac.jp.
authors.forename: Hironori
authors.initials: H
authors.lastname: Haga
authors.forename: Eiji
authors.initials: E
authors.lastname: Katsuyama
mesh_terms: D000328:Adult; D000077548:Anaplastic Lymphoma Kinase; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000175:diagnosis* / Q000378:metabolism / Q000601:surgery; D006801:Humans; D007124:Immunoenzyme Techniques; D017404:In Situ Hybridization, Fluorescence; D007249:Inflammation / Q000175:diagnosis* / Q000378:metabolism / Q000601:surgery; D047708:Myofibroma / Q000175:diagnosis* / Q000378:metabolism / Q000601:surgery; D011379:Prognosis; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000601:surgery
chemical_list: D014408:Biomarkers, Tumor; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases