Inflammatory myofibroblastic tumor of the central nervous system: clinicopathologic analysis of 10 cases.

To verify the pathologic features, anaplastic lymphoma kinase (ALK) expression and biologic behavior of inflammatory myofibroblastic tumors (IMTs) of the central nervous system (CNS), we analyzed 10 cases of IMTs-CNS (8 cranial, 1 spinal, and 1 orbital). Our series of IMTs of the CNS showed a male predominance (male:female = 6:4) and a wide age range (10-60 years; mean age, 46.7 years). Lesion location also varied, but they were basically dura-based. Radiologically, they showed two patterns: isolated mass forming (n = 6) and an en plaque-like pattern (n = 4). Histopathologically, plasma cell granuloma (PCG)-like (n = 5) or fibrohistiocytic (FHC) variant (n = 5) was present. No correlation was found between the radiologic and histopathologic patterns. Spindle-shaped mesenchymal cells of IMTs expressed smooth muscle actin (SMA) in all cases. ALK expression was not found in our IMTs of the CNS. Late recurrence was found in 2 cases in different sites (20%). Pathologically, IMT-CNS could be subclassified into PCG-like and FHC. Immunostaining for SMA was found to helpfully discriminate myofibroblastic cells and to make a differential diagnosis. Although our cases did not show ALK immunoreactivity, some IMTs-CNS can recur, which suggests the neoplastic potential of these tumors. The rearrangement of the ALK gene in IMTs-CNS should be verified by an examination of more cases.