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Orbital lipoma
Key points
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Definition: Orbital lipomas (OL) are very rare tumors that are usually benign, accounting for less than 1% of orbital tumors.
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Classic clue: The patient presents with a well-circumscribed homogeneous orbital mass with low attenuation approximating orbital fat, having no calcifications or fluid-fluid level suggestive of a dermoid or teratoma.
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True primary OLs are as uncommon as extraorbital lipomas are common.
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While usually having a benign course, an OL has been reported to cause blindness in a patient with an intracanalicular lipoma.
Imaging
Computed tomography features
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Computed tomography (CT) is the less preferred imaging option but may be the first study performed, particularly if the lesion is an incidental finding.
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Orbital radiation is undesirable.
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Lesions show characteristic low attenuation masses with values of Hounsfield units similar to normal fat.
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Lesions are usually conspicuous unless they are adjacent to normal intraorbital fat.
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May demonstrate delicate spiderlike thin internal septations.
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No raised calcium or fluid-fluid levels are evident.
Magnetic resonance imaging features
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Preferred imaging procedure with Gd and fat sat.
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Better at defining disease extent.
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Allows sequential follow-up without increasing patient’s cumulative radiation dose.
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OL has high magnetic resonance imaging (MRI) T1 signal similar to orbital fat. Low T1 MRI signal with fatsuppression.
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T2 signal in OL may be inseparable from adjacent orbital hemorrhage.
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Usually nonenhancing with Gd but may have heterogeneity and enhancement if other tissue elements are present.
Clinical issues
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