An inflammatory myofibroblastic tumor in liver with ALK and RANBP2 gene rearrangement: combination of distinct morphologic, immunohistochemical, and genetic features

SummaryInflammatory myofibroblastic tumor is an intermediate-grade neoplasm with potential for recurrence and rare metastasis. Rearrangement of the anaplastic lymphoma kinase gene with variable fusion partners and anaplastic lymphoma kinase expression using immunohistochemistry are noted in about half of the tumors. We present a hepatic inflammatory myofibroblastic tumor from a 34-year–old man with an unusual rearrangement between the Ran binding protein 2 and anaplastic lymphoma kinase genes, as well as a peculiar round cell transformation of tumor cells and a unique nuclear membrane expression of anaplastic lymphoma kinase protein. As the fourth reported inflammatory myofibroblastic tumor with this fusion so far, we find that these genetic and morphologic features may be related to a poor clinical outcome. The diagnostic difficulty and other prognostic factors of inflammatory myofibroblastic tumor are also discussed.