[Lymphocytic infiltrations of the orbit in MRT and CT. Lymphoma, pseudolymphoma and inflammatory pseudotumor]

Orbital Tumors-Clinical, Radiologic and Histopathologic Correlation

Orbital masses include a broad spectrum of benign and malignant entities. Often these masses are asymptomatic or show a slow growth rate, so that emergence of clinical symptoms is prolonged. In this context, cross-sectional imaging plays an elementary role in the characterization of these lesions. Aside from the characterization of the underlying entity, an evaluation of the involved compartments is possible by sufficient imaging, which also facilitates optimal treatment and surgery planning. The purpose of this review is to explore different benign and malignant orbital tumors and their typical appearance in imaging together with histopathologic findings.

Orbital masses: CT and MRI of common vascular lesions, benign tumors, and malignancies

A wide variety of space occupying lesions may be encountered in the orbit. CT and MR imaging frequently help confirm the presence of a mass and define its extent. Characteristic imaging features may help distinguish among lesions that have overlapping clinical presentations. This review focuses on some of the common orbital masses. Common vascular lesions that are reviewed include: capillary (infantile) hemangioma, cavernous hemangioma (solitary encapsulated venous-lymphatic malformation), and lymphangioma (venous-lymphatic malformation). Benign tumors that are reviewed include: optic nerve sheath meningioma, schwannoma, and neurofibroma. Malignancies that are reviewed include: lymphoma, metastasis, rhabdomyosarcoma, and optic glioma. Key imaging features that guide radiological diagnosis are discussed and illustrated.

Magnetic resonance imaging of orbital tumors

This contribution provides an overview of diseases of eye and orbit and their appearance on magnetic resonance imaging. In recent years the diagnosis of eye and orbit pathology has profited significantly from increasingly sophisticated technical developments in the field of tomographic methods. Due to the small size of the examination area the improvement in spatial resolution and soft tissue contrast leads to an increase in image quality. In most clinical questions concerning eye and orbit pathologies magnetic resonance imaging is superior to computed tomography and should be early performed.

[Appearance of orbital diseases on MRI]

We provide an overview of diseases of the orbit and their MR imaging appearance. Over recent years MRI has become established in the diagnosis of orbit diseases. There is a selection of different surface coils for examination. The choice of surface coil depends on the clinical question and the anatomical region under consideration. In addition, the significance of the different sequences and the value of contrast medium administration are discussed.

MRI patterns in orbital malignant lymphoma and atypical lymphocytic infiltrates

OBJECTIVE

To evaluate the potential of MRI in differentiating between malignant lymphomas and atypical lymphocytic infiltrates in the orbit.

MATERIALS AND METHODS

MRI, clinical and histopathological findings in 30 patients presenting with orbital lymphoproliferative diseases (malignant lymphoma and atypical lymphocytic infiltrates) were evaluated.

RESULTS

MRI detected 28 out of 30 (93%) orbital lymphoid tumors. Seven out of eight (87.5%) atypical lymphocytic infiltrates and 21/22 (95.4%) of malignant lymphomas were detected. One conjunctival malignant lymphoma and one conjunctival atypical lymphocytic infiltrate were missed. Only malignant lymphoma lesions were hyperintense compared to the extraocular muscles on precontrast and postcontrast T1-weighted images. The lacrimal duct was involved only with malignant lymphoma. Bilateral disease was more likely to be malignant lymphoma. Intraconal lesions were more likely to be associated with lesions elsewhere. No malignant lymphoma involved the extraconal fat. Only intraconal atypical lymphocytic infiltrates had indistinct margins.

CONCLUSION

In the orbit, MRI features alone may not allow clear-cut differentiation of malignant lymphomas from atypical lymphocytic infiltrates. However, certain imaging features increase the likelihood of distinguishing them. MRI may miss conjunctival disease. Both orbits should be imaged when orbital lymphoid disease is a probability. The presence of intraconal disease should prompt a search for lesions elsewhere. The use of a head coil instead of a superficial coil may be advantageous by eliminating coil shine effect and allowing evaluation of both orbits. Comparison of lesion signal to extraocular muscle signal appears to be a better alternative than cerebral gray matter or periorbital fat in differentiating malignant lymphoma from atypical lymphocytic infiltrates. Since imaging findings overlap, histopathological diagnosis is necessary in all cases.

Management of orbital tumors

Orbital tumors are uncommon. In children, both malignant and benign causes of orbital proptosis necessitate urgent assessment; in many cases, emergent intervention is necessary to avoid blindness. In adults, proptosis is most commonly associated with thyroid orbitopathy. Orbital tumors in adults rarely are characterized by the explosive growth and damage that can occur with childhood lesions. In both age-groups, the evolution of better scanning modalities, such as magnetic resonance imaging with fat saturation and gadolinium enhancement, has improved diagnostic accuracy, especially in patients with loss of vision. In more than 95% of cases, noninvasive techniques yield a correct diagnosis. In patients who require nonsurgical intervention, especially if the diagnosis is uncertain, fine-needle aspiration biopsy has an accuracy that exceeds 95%. Combined-modality therapy has improved the control of and decreased the morbidity associated with several orbital tumors. Surgical advances, such as the ancillary use of the CO2 laser, have enhanced the management of some orbital tumors.