Inflammatory myofibroblastic tumor involving the central nervous system

Inflammatory myofibroblastic tumor (IMT) is a distinct mesenchymal neoplasm that arises in the lung, soft tissues and a variety of organs. In the past, morphologic and conceptual overlap with inflammatory pseudotumor, a presumed inflammatory lesion, has been described in the literature. However, demonstration of ALK gene rearrangements in a subset of cases supports the concept of a distinct neoplastic entity. In rare instances, it may involve the central nervous system, and present as a dural based mass mimicking meningioma. IMT has variable clinical behavior but may also behave in a malignant fashion in a proportion of cases. Interestingly, multicentricity has also been described with IMT. We discuss the case of a 30-year old woman who developed a well circumscribed intracranial mass interpreted preoperatively as a meningioma. Histologic examination demonstrated IMT containing an ALK rearrangement. The neoplasm was morphologically similar to a lung neoplasm resected 31 months previously. We use this case study as an opportunity to discuss the differential diagnosis of IMT with a focus on intrancranial locations and useful ancillary techniques in approaching the pathologic diagnosis.