Fig. 8.

Orbital eRMS with involvement of the roof of the orbit, a rare form of orbital RMS, in an 8-year old boy, presenting with orbital pain and proptosis. The bone invasion classifies the tumour as parameningeal, with a worse prognosis compared to orbital RMS. a Coronal post-contrast SET1 image shows a large, strongly enhancing lesion within the roof of the right orbit, extending into the superior extraconal compartment (open arrow), suggesting a primary bone tumour. Displacement of the eye ball downward and laterally. b Additional CT (coronal multiplanar reconstruction after i.v. contrast) confirmed bone involvement and local destruction with intraorbital extention (arrow). From the imaging it was impossible to differentiate between a primary bone tumour (MRI) or a primary (atypical) orbital location with adjacent bone invasion (CT). The location is not characteristic for RMS, which most often is within the medial quadrant. At surgery the lesion was considered a primary bone location. Histology: e-RMS