2016 Volume 53 Issue 3 Pages 289-293
Inflammatory myofibroblastic tumor (IMT) is considered to be a neoplasm on the basis of the clonal rearrangement of the ALK gene in half of all patients. However, when ALK rearrangement is negative, it is difficult to distinguish IMT from inflammatory pseudotumor (IPT) owing to their similar pathological features. We encountered a 7-year-old boy who developed left facial and abducens nerve palsy. Diagnostic imaging revealed a mass lesion in the left masticatory space. HE and immunological staining of a tumor biopsy specimen showed the proliferation of spindle cells and the infiltration of inflammatory cells that were ALK negative. ALK rearrangement was undetectable in in situ hybridization. Karyotypic analysis of the biopsy sample showed the chromosomal translocation of t(1;11)(q32;q23) in 5 of 20 mitoses, leading to the diagnosis of IMT. The patient was treated with chemotherapy including cyclophosphamide, vincristine, pirarubicin and cisplatin, and the tumor effectively regressed thereafter. No recurrence has been observed 3 and a half years after the completion of chemotherapy. In this patient, we showed the usefulness of the karyotypic analysis of a tumor specimen to distinguish IMT from IPT, and revealed t(1;11)(q32;q23) to be a potential chromosomal translocation involved in the pathogenesis of IMT.
