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.