An orbital amyloidosis misdiagnosed as cavernous hemangioma

A 43-year-old man was admitted to our hospital due to a mass in the left orbit for a month. He had progressive, painless vision loss in his left eye for 5 years, along with occasional dizziness. His routine laboratory tests were within normal limits. Magnetic resonance imaging (MRI) presented a mass with a size of 2.8 cm × 2.5 cm × 1.7 cm in the left orbit. The mass was mainly located in the outer space of the muscle cone and grew into the muscle cone. The lesion showed iso-signal intensity on T1-weighted imaging (T1WI), and nodular low signal intensity was noted in the lesion (Fig. 1A). The sagittal T1-weighted scan showed that the eyeball was partially surrounded by the mass, with unclear boundaries from the superior rectus muscle and clear boundaries from the optic nerve (Fig. 1B). Fat-suppressed T2-weighted imaging showed mixed high signal intensity (Fig. 1C). The contrast-enhanced scan of the lesion showed inhomogeneous mildly enhancement and the optic nerve signal was not abnormal (Fig. 1D). The lesion was resected with left lateral orbital orbitotomy. The lesion developed in the superior rectus muscle. The soft tissues surrounding the lesion and optic nerve were not involved. Postoperative pathology showed that a large number of eosinophilic deposits, surrounded by a large number of multinucleated giant cells. Congo red staining was positive (Fig. 2A-B). Pathological features of the lesion supported a diagnosis of amyloidosis.