Primary perineal alveolar rhabdomyosarcoma metastatic to an extraocular muscle.

A 17-year-old boy diagnosed with an alveolar rhabdomyosarcoma involving the perineum and with extensive lymphadenopathy was treated with chemotherapy yet developed metastases to the head and neck 6 months into therapy. Ten months after initial diagnosis, while receiving salvage chemotherapy and radiotherapy, he returned with pain on movement of his left eye, proptosis, and ptosis of the left upper eyelid. Computed tomography (CT) revealed a mass within the left lateral rectus muscle that biopsy confirmed to be metastatic alveolar rhabdomyosarcoma. Despite continued chemotherapy and radiotherapy, he ultimately died of the disease. Alveolar rhabdomyosarcoma from distant sites rarely metastasizes to the extraocular muscles. However, our case shows that alveolar rhabdomyosarcoma may metastasize to the orbit and involve a single muscle.