Presentation
Left eye proptosis and orbital swelling.
Patient Data
A large exophytic left orbital soft tissue extraconal mass seen arising from the superior aspect of the orbital cavity, inseparable from the superior oblique muscle.
The mass causes mass effect upon the adjacent structures; displacing the muscles anteroinferior causing proptosis of the globe, stretching the optic nerve and deforming the superior aspect of the orbital cavity, extending to the preseptal compartment, without definite bone involvement or posterior orbital canal extension.
The mass appears isointense to adjacent muscles on T1WI, and hyperintense on T2WI with areas of signal void and areas of restricted diffusion, showing avid post-contrast enhancement.
The remainder of the orbit is unremarkable, and the contralateral orbit is normal.
The patient went on to have an excision confirming the diagnosis of an anaplastic orbital rhabdomyosarcoma.
Case Discussion
Rhabdomyosarcoma is a highly malignant tumor and is one of the few life-threatening diseases. It is the most common soft-tissue sarcoma of the head and neck in childhood with 10% of all cases occurring in the orbit. Rhabdomyosarcoma has been reported from birth to the seventh decade, with the majority of cases presenting in early childhood.
Orbital rhabdomyosarcoma is usually extraconal (37–87%) or both intra- and extraconal (13–47%), and more commonly superonasal in location especially for embryonal rhabdomyosarcoma (inferior location is more common for alveolar).
The mass is usually close to extraocular muscles, but there is no enlargement of the muscle belly. In the early stages, the tumor is well circumscribed, but in later stages, where there is pseudocapsular invasion, the borders are irregular. There may be some bone deformity, but frank bone destruction with bone involvement is rare, and the diagnosis, in this case, will change from orbital to parameningeal RMS. The tumor may show hemorrhages and cyst formation