From the archives of the AFIP: Pediatric orbit tumors and tumorlike lesions: nonosseous lesions of the extraocular orbit.

The histologic spectrum of nonosseous tumors and tumorlike lesions of the extraocular orbit in children differs from that in adults, and the appearance of these lesions at imaging reflects their pathologic features. Rhabdomyosarcoma is the most common extraocular orbital tumor in children. This neoplasm usually manifests in young children, grows quite rapidly, and is fairly vascular. Vasculogenic lesions are common orbital lesions in newborns and young infants. The most prevalent of these are infantile hemangioma, a true neoplasm, and venous-lymphatic malformation, a developmental anomaly. Hemangioma is quite vascular, has a predictable course of proliferation followed by slow involution, and is distinguished on magnetic resonance images by the finding of flow voids within the mass and at its periphery. Venous-lymphatic malformation in the orbit is an anomaly of venous and lymphatic development that is characterized by unenhancing, cystic lymphatic and enhancing, solid venous components. Intralesional hemorrhage is common and frequently produces distinctive fluid-fluid levels within the cystic portions. Unlike hemangiomas, venous-lymphatic malformations grow with the patient and never involute spontaneously. Infantile fibromatosis is one of the fibromatoses and affects newborns and young infants. The tumor is nodular and composed of a zonal architecture, with frequent hemorrhage or necrosis in the central portion, characteristics that confer a target appearance at imaging. These lesions usually stop growing or spontaneously regress. All of these extraocular masses typically manifest with proptosis, and imaging differentiation is desirable because the treatments and prognoses vary greatly.