Absence of anaplastic lymphoma kinase-1 expression in inflammatory myofibroblastic tumors of the central nervous system: Does it signify a different nosologic entity from its systemic counterpart?

Background and Aim: Inflammatory myofibroblastic tumors (IMFTs) are uncommon neoplasms of the central nervous system (CNS) of intermediate grade biologic potential. Anaplastic lymphoma kinase (ALK-1), a diagnostic marker of anaplastic large cell lymphoma, is also expressed in a subset of IMFTs and appears to have prognostic significance. Though, few studies have evaluated expression of ALK-1 in IMFTs of the CNS. This retrospective study was undertaken to evaluate the expression of ALK-1 expression in IMFT of CNS by immunohistochemistry and correlate with the clinical, radiological and pathologic features. Materials and Methods: Five cases diagnosed as IMFT/inflammatory pseudotumour/plasma cell granuloma, diagnosed in CNS over 10 year period (1998-2007) were retrieved from the archives of Department of Neuropathology of a tertiary referralcenter. The clinical profile and imaging features were collected from the case records. Hematoxylin and eosin stained sections were reviewed with immunohistochemistry for smooth muscle actin (SMA), vimentin, desmin, ALK-1, p53, MIB-1, CD68, leukocyte common antigen, CD3, and CD20. Results: All five cases of IMFTs presented as dural-based space occupying or en-plaque lesions. Histologically, four cases had combined plasma cell granuloma-fibrous histiocytoma morphology, and one had fibrous histiocytoma-like morphology. Immunohistochemically, SMA was strongly positive in spindle cell component of the tumors confirming diagnosis. ALK-1 expression could not be detected by immunohistochemistry in any of the cases. Conclusion: Further studies analyzing ALK-1 gene mutation and rearrangements are required to determine pathogenetic role, if any, in CNS IMFTs.