The most common malignant tumor of the orbit in childhood is now believed to be the rhabdomyosarcoma, a rapidly growing neoplasm composed of partially differentiated striated muscle cells.1-3 The growth arises from primitive tissue rather than from adult muscle and may originate within the orbit as well as in other sites throughout the body. The remarkable simultaneous appearance of this malignancy in the orbits of two brothers has prompted this report.
Rhabdomyosarcoma of the orbit was recently reviewed by Porterfield and Zimmerman, who collected 55 cases3; other smaller series exist, such as those by Calhoun and Reese,4 Horn and Enterline,5 Blaxter and Smith,6 Frayer and Enterline,2 and others. No complete review is attempted here.
The average age of onset is seven to eight years, and the tumor occurs more frequently in boys than in girls. The lesion is unilateral and usually begins in the