Ewing sarcoma presenting as a subconjunctival mass

A 14-year-old previously healthy boy presented for evaluation of a subconjunctival mass that had been present for 2 to 3 years, but had recently started to enlarge. Imaging demonstrated an anterior orbital lesion that enhanced with gadolinium. An excisional biopsy was performed and revealed highly malignant-appearing small, blue, round tumor cells. Immuohistochemical stains were strongly reactive with CD99 (MIC2 and O13), CD56, and retained INI-1 reactivity. The EWS-FLI1 chimeric fusion gene transcript was also detected by reverse transcription-polymerase chain reaction analysis, confirming Ewing sarcoma. Full-body CT, bone scan, and bone marrow biopsy were all negative, proving this to be a premetastatic, primary orbital tumor arising from soft tissue.