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Abstract
The complex of neuro-sensory, vascular, motor and secortory structures within the orbit is commonly affected by wide variety of orbital mass disease.
The effect of any orbital mass is governed not only by the nature of the process but also by the anatomic pattern of involvement (Location of the mass).
Five pathophysiologic processes can occur either indepently or in combination, within and around the orbit.
It is useful to look at the occurrence of orbital mass lesions within the broad age groups of childhood, a dolescence, middle adult life and the elderly.
Some orbital masses are restricted to one or more common in ceratin orbital areas and this information can provide a context for differential diagnosis based on location.
The major clinical processes that can be identified on examination of a patient with orbital mass disease are mass effect, inflammation, infiltration or a vascular features of the disease.
The appearance of broad categories of orbital mass lesions by the recent imaging modalities form a basis for differential diagnosis.
CT provides excellent soft tissue resolution due to the presence of orbital fat which of low density. It is the technique of choice for primary assessment of orbital mass lesions, it provides details of bony anatomy so it plays a dominant role in patients with orbital trauma as well as foreign bodies and calcification.
MRI is very useful for demonstrating hemorrhage within lesions. There is some recent evidence that MRI may distinguish idiopathic inflammation from lymphoid tumors. Both CT and MRI are extremely useful in imaging optic nerve lesions, idiopathic orbital inflammation and thyroid orbitopathy.
The pathologic process in the orbit mirror those in the rest of the body and also include some entities that have predilection for this site. from histopathologic point of view, orbital neoplasms include, neoplasm of epithelial origin, neoplasm of mesenchymal origin, neoplasm of lymphoproliferative origin, leukemic neoplasm, melanocytic neoplasm central nervous system neoplasm, neoplasm of orbital bone, neoplasm of lacrimal gland and optic nerve neoplasm.