Inflammatory Myofibroblastic Tumor Affecting the Maxilla: Case Report and Immunoexpression of ALK and Igg4

Inflammatory myofibroblastic tumor (IMT) is a rare lesion of unknown etiology, often affecting the lungs. In the head and neck region, it has a predilection for the paranasal sinuses. Microscopically, IMT presents (myo)fibroblastic proliferation with varying degrees of inflammatory cell infiltrate. Here, we present an IMT affecting the maxilla of a 27-year-old woman. Periapical and panoramic radiography showed a well-defined radiolucent area. Surgical excision of the whole lesion was performed. Histopathologic analysis revealed a benign spindle-cell proliferative process admixed with a chronic inflammatory infiltrate. Immunohistochemical analysis showed positivity for α-SMA and IgG, whereas CK, EMA, S100, CD34, and remarkably ALK and IgG4, were negative. Ki-67 labeling index was less than 1%. A diagnosis of IMT was made. ALK-negative IMTs are not uncommon (one-third of cases), and IgG4 negativity reinforces the suggestion that IMT does not belong to the spectrum of IgG4-related diseases, in contrast to most inflammatory pseudotumor cases.