A 54-year-old woman presented for evaluation of a left orbital mass, which had been incidentally found on computed tomography for sinusitis. She was asymptomatic except for 2 years of progressive, painless, left-sided proptosis. Her physical examination findings were unremarkable except for resistance to retropulsion of the left globe and 5 mm of left-sided proptosis by Hertel exophthalmometry.
MRI revealed a superonasal orbital mass that was T1 isointense to brain parenchyma and heterogeneously T2 hyperintense (Figure 1A), with a small cystic component and avid peripheral contrast enhancement (Figure 1B). Bony remodeling without destruction was noted, as well as displacement of the superior oblique and superior rectus muscles.
The interpreting radiologist thought that the mass did not have the typical appearance of a vascular malformation or of a schwannoma and that other neoplastic and chronic infectious causes, including a parasitic origin, should be considered.
Because of the diagnostic uncertainty, the orbital mass was biopsied. Intraoperatively, the tumor was found to consist of a firm, thick, whitish cortex with a clear myxoid fluid in its center.
Histopathologic examination revealed regions of solid spindle-shaped cells that immunostained strongly for vimentin and S100 (Antoni A pattern) and were intermixed with areas of Alcian blue–positive myxoid stroma (Antoni B pattern) (Figure 2).
Some cells had large, irregularly shaped, atypical-appearing nuclei (Figure 2, inset); however, no mitoses were seen and the proliferative index with Ki-67 immunostaining was low. These histologic features are consistent with a schwannoma with degenerative (ancient-type) changes.
Final Diagnosis: Cystic schwannoma with ancient-type (degenerative) changes