An inflammatory myofibroblastic tumor exhibiting immunoreactivity to KIT: a case report focusing on a diagnostic pitfall

作者：Kataoka Tatsuki R; Yamashita Nobuhiro; Furuhata Ayako; Hirata Masahiro; Ishida Takaki; Nakamura Ichiro; Hirota Seiichi; Haga Hironori^*; Katsuyama Eiji

来源：World Journal of Surgical Oncology, 2014, 12(1): 186.

DOI：10.1186/1477-7819-12-186

• Anaplastic lymphoma kinase
• Differential diagnosis
• FISH
• Gastrointestinal stromal tumor
• Inflammatory myofibroblastic tumor
• KIT
• Urinary bladder

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 a, 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.

• 出版日期2014-6-18