Orbital Schwannoma: Radiographic and Histopathologic Correlation in 15 Cases.

PURPOSE: To evaluate the relationship between radiographic and histopathologic features of orbital schwannoma.

METHODS: Retrospective review of 15 patients with orbital schwannoma managed at an ocular oncology service.

RESULTS: The mean patient age at the time of presentation was 42 years old (median 40, range 15-64 years). The orbital schwannoma was found incidentally (n = 2) or with symptoms of proptosis (n = 2), blurred vision (n = 3), pain (n = 3), eyelid swelling (n = 2), diplopia (n = 2), or headache (n = 1). The mean duration of symptoms was 15 months (median, 9; range 1-60 months). The tumor occupied the superior (n = 11) or inferior (n = 4) orbit. Antero-posterior tumor location involved the anterior (n = 2), middle (n = 3), posterior (n = 4), or entire (n = 6) orbit. MRI was performed in 12 patients (80%) and CT was the only form of imaging in 3 patients (20%). The T1-weighted MRI (n = 11) showed the mass as isointense (n = 10) or hyperintense (n = 1) to the extraocular muscles). On T2-weighted MRI (n = 10), the mass demonstrated hyperintensity (n = 9) or hypointensity (n = 1). Histopathologic assessment demonstrated Antoni A (n = 12) and Antoni B (n = 12) patterns. Antoni A pattern correlated with hyperintensity on T1-weighted MRI and hypointensity on T2-weighted MRI. Antoni B pattern correlated with hypointensity on T1-weighted MRI and hyperintensity on T2-weighted MRI. As Antoni B approached >50% of the solid mass (n = 8), both T1- and T2-weighted MRI images were more likely to be heterogeneous (n = 7, 88% and n = 6, 75%, respectively).

CONCLUSION: Orbital schwannomas are nearly always benign, well-encapsulated slowly progressive tumors. Due to the biphasic distribution of Antoni A and Antoni B pattern, the appearance on MRI has a variable degree of heterogeneity. Antoni A pattern correlated with hyperintensity and Antoni B pattern correlated with hypointensity on T1-weighted MRI.