Orbital schwannoma: correlation of magnetic resonance imaging and pathologic findings.

PURPOSE

To report the correlation between magnetic resonance imaging (MRI) findings and histopathology of orbital schwannomas.

METHODS

This study is a retrospective noncomparative interventional case series of three consecutive patients with orbital schwannoma. After preoperative MRI, all patients underwent orbitotomy and tumor removal. Histopathologic and immunopathologic studies of the excised tumors were performed. The main outcome measures were MRI features, histopathology, and their relationship to the cohesiveness of the tumor.

RESULTS

The patients' ages were 56 years (patient 1), 43 years (patient 2), and 18 (patient 3) years. MRI demonstrated that the tumors were well-circumscribed, intraconal in patient 1, superior extraconal in patient 2 and inferotemporal extraconal in patient 3. The tumor in patient 1 had a partly cavitary appearance, while the tumors in patients 2 and 3 had a solid appearance on MRI. The tumor had heterogeneous signal intensity in patients 1 and 2 and homogeneous signal intensity in patient 3 on T2-weighted images. All patients underwent orbitotomy and tumor removal. In patients 1 and 2, the tumor was gelatinous and fragmented during removal. The fragments were completely excised in patient 1 and an incomplete piecemeal tumor excision was made in patient 2. In patient 3, complete excision without fragmentation was performed. Pathologic examination revealed that the tumor was of Antoni B pattern in patient 1, mixed Antoni A and B patterns in patient 2, and marked Antoni A pattern in patient 3. At a mean follow-up of 23.7 months (range: 22-26 months) after surgery, all patients retained preoperative visual acuity. Patient 2 developed recurrence at 21 months follow-up and underwent Krönlein orbitotomy for excision of the recurrent tumor.

CONCLUSIONS

MRI is useful in depicting both the anatomic location and internal consistency of orbital tumors. Schwannomas with MRI evidence of cavitary change or heterogeneous signal intensity on T2-weighted images were found to have marked Antoni B pattern on histopathology, imparting a friable structure and fragmented excision.