Alveolar soft-part sarcoma of the orbit.

An 11-month-old white female with a three-month history of swelling of soft tissue around the right eye presented with a proptotic globe and marked limitation of motility. A CT scan showed a soft-tissue mass in the orbit, which was biopsied and examined by light and electron microscopy. The specimen consisted of large polygonal and cuboidal cells of uniform appearance arranged in pseudo-alveoli around capillaries. The nuclei were pale and ovoid with prominent nucleoli and rare mitoses. The cytoplasm was packed with lipid droplets and the paranuclear region contained clusters of periodic acid-Schiff (PAS)-positive, diastase-resistant granules and needle-shaped crystals, which showed a linear periodicity of 100 nm by electron microscopy. These cytoplasmic crystals, which were diagnostic for alveolar soft-part sarcoma, were also found to be acid phosphatase-positive and, therefore, components of the lysosomal system. A lid-sparing exenteration of the right orbit was performed, and subsequent radiation therapy by cesium implant delivered 24,000 rads to the operative site. The patient is alive at 22 months following initial biopsy with no evidence of tumor recurrence.