Orbital neoplasms in adults may be categorized on the basis of location and histologic type. Imaging features of these lesions often reflect their tissue composition. Cavernous malformations (also known as cavernous hemangiomas), although not true neoplasms, are the most common benign adult orbital tumor. They typically appear as a well-circumscribed, ovoid intraconal mass on cross-sectional images. Lymphoma, which may be primary or secondary to systemic disease, is the most prevalent orbital neoplasm in older adults (≥60 years of age). Choroidal melanoma is the most common primary adult ocular malignancy. Melanin has intrinsic T1 and T2 shortening effects, classically manifesting with hyperintense signal on T1-weighted magnetic resonance (MR) images and with hypointense signal on T2-weighted images. However, amelanotic or mildly pigmented lesions of melanoma do not demonstrate these characteristic MR imaging features. Breast cancer is the most common malignancy to metastasize to the orbit, followed by prostate cancer, melanoma, and lung cancer. In women with bilateral enophthalmos, metastatic scirrhous breast cancer should be considered in the differential diagnosis. Neoplasms that arise from the optic nerve or its sheath include glioma and meningioma. At imaging, gliomas often cause fusiform expansion of the optic nerve, in which the nerve itself cannot be delineated from the lesion. In contrast, meningiomas classically have a "tram-track" configuration, whereby the contrast-enhancing tumor is seen alongside the optic nerve. Neoplasms that derive from peripheral nerves include schwannoma and neurofibroma, the latter of which is associated with neurofibromatosis type 1. MR imaging is particularly valuable for evaluation of orbital neoplasms, as it provides critical anatomic information about ocular structures involved, perineural spread, and intracranial extension.

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