Sarcoma is a tumor that arises from soft tissue, connective tissue, and bone. A subtype, rhabdomyosarcoma, is a highly malignant neoplasm of mesenchymal tissue. It most often occurs in children, in which it is the most common soft tissue sarcoma and represents 5% of all childhood cancers.1, 2 The average age of onset is 7–8 years old, with peak incidences in the age groups of 2–5 and 15–19 years (although this second peak is for males only). 3 However it can occur in all age groups including infants and adults, being reported in individuals up to 56 years old.4, 5, 6 It is slightly more common in males with a male:female ratio of 5:3. The overall incidence is 4.3 cases per million children per year;7 approximately 250 new cases are seen in the United States each year.8
Rhabdomyosarcoma may occur throughout the body, but is most often seen in the head and neck region (approximately 45% of cases). It may also involve the trunk (40%), or extremities.9 Of cases involving the head and neck, 25–35% occur in the orbit, 50% in parameningeal sites, and 25% in other locations.9 Overall, the orbit is the primary site for rhabdomyosarcoma in approximately 10% of cases.
Orbital rhabdomyosarcoma represents the most common orbital malignancy of childhood, and accounts for 4% of orbital masses in children (by far the most common orbital mass in children is a dermoid cyst).10, 11 Fortunately, compared to other sites the orbit has a more favorable prognosis with a 5-year survival greater than 85% with advances in recognition and treatment.12
Although rare, it is critical that eye care professionals recognize orbital rhabdomyosarcoma.13 In addition to being one of few life-threatening conditions to present to the eye care professional, it may mimic other conditions such as preseptal cellulitis leading to diagnostic delay.