Rhabdomyosarcoma: (1) This tumor of striated muscle is the most common primary malignancy of the orbit in children. Due to its malignant and agressive nature, there is usually a rapid progression of proptosis. Lid edema and erythema may mislead physicians to suspect cellulitis, however, CT scanning reveals a solid mass arising from around an extraocular muscle. Treatment has improved rapidly over the last few decades and consists of radiation and chemotherapy. Intracranial spread is associated with poor prognosis. Back to Orbit