Inflammatory myofibroblastic tumor of the lung and the maxillary region: a benign lesion with aggressive behavior.

Inflammatory myofibroblastic tumor (IMT) is a rare mass-forming lesion characterized by fibroblastic or myofibroblastic spindle cell proliferation with varying degrees of inflammatory cell infiltration. Although it has been reported in virtually every organ in the body, the lung is the most common site of involvement. Extrapulmonary IMTs, although rare, have been reported and are characterized by different, more aggressive behavior. We report an extremely rare case of maxillary metastases of pulmonary IMT. Lung IMT was initially misdiagnosed, and oral lesion mimicked clinically and radiologically a radicular cyst. On histologic examination, cells exhibited diffuse and intense immunoreactivity for α -smooth muscle actin and vimentin whereas both pulmonary and oral IMTs presented absence of cellular atypia and lack of expressivity of oncogenic determinants. Distant metastases of lung IMT are extremely unusual, and this is the first report to our knowledge with this particular clinical course. Despite the possibility that the present case could also represent a metachronous multifocal IMT, with pulmonary and extrapulmonary lesions, similar histopathological and immunohistochemical patterns in lung and maxillary region suggest a metastatic course.