[Endoscopic Endonasal Transethmoidal Biopsy for IgG4-Related Intraorbital Pseudotumor:A Case Report].

Background: We experienced a case of intraorbital pseudotumor associated with IgG4-related disease, for which we successfully performed an endoscopic endonasal transethmoidal biopsy for the intraorbital pseudotumor as well as endoscopic sinus surgery for a refractory pansinusitis at the same time.
Case Report: A 59-year-old man was referred to our hospital because of an intraorbital mass lesion. MRI showed 2 mass lesions:a large intraconal lesion encasing the left optic nerve on the orbital apex, and a small extraconal lesion medial to the left medial rectus muscle extending into the anterior ethmoid canal. In addition, CT showed severe pansinusitis. A blood test showed a marked elevation of IgG4. IgG4-related pseudotumor was suspected, but IgG4-related MALT lymphoma was an alternative diagnosis, and a biopsy of the mass lesion was required. We successfully performed both, an endoscopic endonasal transethmoidal biopsy for the mass lesion and endoscopic sinus surgery for the refractory pansinusitis at the same time. The pathological diagnosis was an IgG4-related pseudotumor.
Conclusion: Endoscopic endonasal transethmoidal biopsy is an effective and minimally invasive method for making a definitive diagnosis of IgG4-related intraorbital pseudotumor. Using this method, refractory pansinusitis frequently associated with this disease can be treated. For successful treatment, interdisciplinary decision making and collaborative team surgery are crucial.