ORBITAL RHABDOMYOSARCOMA - THE RADIOLOGICAL CHARACTERISTICS

We reviewed computed tomography (CT) studies in 30 patients with histo logically confirmed orbital rhabdomyosarcoma. There were 17 male and 1 3 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 comp artments in 14 (47%) cases; it was solely extraconal in 11 (37%) and i ntraconal in five (16%), Within the orbit the upper inner quadrant was the most common site, 20 (67%) of the tumours lying in this region. M ore than one quadrant was involved in 16 (53%) cases. The epicentre of the tumour was in the eyelids of three (10%) patients. At presentatio n the mean size of the mass was 25 x 17 mm in long and short axis diam eters, respectively. The tumours were of soft tissue density with mode rately well defined margins and an irregular shape. They showed mild t o moderate contrast enhancement, Calcification was seen in one case. C hanges in the adjacent bone were seen in at least 12 (40%) patients. I ntracranial extension was present in one (3%) patient and invasion of the paranasal sinuses was also seen in one (3%) patient. The intraorbi tal structures were displaced or encased by the tumour mass. The globe was displaced and distorted but not invaded by the tumour. Magnetic r esonance 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.