Orbital histiocytic sarcoma in a 2-year-old child.

Histiocytic sarcoma (HS) is an exceedingly rare hematologic malignancy that typically presents in the skin, gastrointestinal tract, and lymph nodes. Few cases of HS have been reported in the head and neck. This study describes the case of a 2-year-old girl presenting with 2 weeks of left lower eyelid swelling. Diagnostic testing and biopsy revealed a large inferior orbital mass causing severe bony destruction with extension into the sinuses. Pathologic analysis revealed classic features of HS. To the best of knowledge, no previous case of HS occurring in the orbit of a child has been reported. This study presents an exceedingly rare case of HS in a young child presenting with eyelid swelling. In addition, this case report is in compliance with HIPAA regulations.