Alveolar rhabdomyosarcoma presenting as an acute orbital mass in the medial rectus muscle.

Rhabdomyosarcoma is the most common pediatric primary neoplasm in the orbit, often presenting with rapid proptosis and orbital symptoms. We describe a 15-year-old girl who presented with an acute mass in her medial rectus muscle that was subsequently diagnosed as widely disseminated alveolar rhabdomyosarcoma. To our knowledge, this represents the first reported case in which an enlarged extraocular muscle was the initial manifestation of disseminated alveolar rhabdomyosarcoma.