Orbital rhabdomyosarcoma--the radiological characteristics

We reviewed computed tomography (CT) studies in 30 patients with histologically confirmed orbital rhabdomyosarcoma. There were 17 male and 13 female patients, mean age 8.8 years (median age 7 years, age range 1 month to 51 years). The tumour occupied the intra and extraconal compartments in 14 (47%) cases; it was solely extraconal in 11 (37%) and intraconal in five (16%). Within the orbit the upper inner quadrant was the most common site, 20 (67%) of the tumours lying in this region. More than one quadrant was involved in 16 (53%) cases. The epicentre of the tumour was in the eyelids of three (10%) patients. At presentation the mean size of the mass was 25 x 17 mm in long and short axis diameters, respectively. The tumours were of soft tissue density with moderately well defined margins and an irregular shape. They showed mild to moderate contrast enhancement. Calcification was seen in one case. Changes in the adjacent bone were seen in at least 12 (40%) patients. Intracranial extension was present in one (3%) patient and invasion of the paranasal sinuses was also seen in one (3%) patient. The intraorbital structures were displaced or encased by the tumour mass. The globe was displaced and distorted but not invaded by the tumour. Magnetic resonance imaging (MRI) studies were also reviewed in five patients. On T1-weighted images the tumour gave a similar signal to muscle but on T2-weighted images it gave a higher signal.