Atypical sino-orbital inflammatory myofibroblastic tumor with bone and cerebral invasion extending to the orbit

Purpose: To report the case of an atypical sino-orbital inflammatory myofibroblastic tumor. Methods: Case report. Results: A 71-year-old man presented slowly progressive painless diplopia followed by unilateral proptosis of the left eye with slight edema of the upper eyelid. Visual acuity was 0.4 with a relative afferent pupillary defect (RAPD). Abduction and depression of the left eye were limited. Imaging showed a left sino-orbital tumor with mass effect on the medial rectus muscle resulting in proptosis. The lesion showed intracranial extension through the superior orbital fissure with bone erosion and sclerotic bone reaction. Endoscopic ethmoidal, maxillary, and orbital biopsies revealed an inflammatory myofibroblastic tumor. Full blood count showed an eosinophilia while antineutrophil cytoplasmic antibodies and C-reactive protein were negative. To date, 7 cases of orbital myofibroblastic tumor have been described, though none of the prior studies have described bone invasion. Conclusions: This erosive sino-orbital inflammatory myofibroblastic tumor is a novel finding mimicking a malignant tumor.