Rhabdomyosarcoma

Epidemiology

Rhabdomyosarcoma is the most common sarcoma in children (84%) and the second most frequent soft tissue tumor arising in the pediatric head and neck (35–45%). The orbit (36%) and nasopharynx (15%) are the most commonly involved sites, followed by middle ear (14%), paranasal sinuses (8%), and paraspinal regions. There is a bimodal peak for age of onset, 2 to 6 years and 14 to 18 years. Boys are affected more commonly, with a male to female ratio of 2:1. The incidence of metastatic cervical adenopathy at the time of presentation ranges from 3 to 25%.

Clinical Findings

Affected children present with a palpable neck mass and neck pain. The orbital tumor produces a rapidly developing unilateral proptosis. Large nasopharyngeal, oropharyngeal, or laryngeal lesions may cause airway obstruction. Nasopharyngeal rhabdomyosarcomas present with rhinorrhea, sore throat, and serous otitis media secondary to eustachian tube obstruction. Intraspinal extension may cause varying neurological deficits.

Pathology

Rhabdomyosarcoma is divided into four separate types: embryonal, botryoid, alveolar, and pleomorphic varieties. The less differentiated embryonal and botryoid types are seen in infants and children. The embryonal rhabdomyosarcoma is the most common (75%) histologic type. The alveolar type is seen in adolescents (20%) and has the worst prognosis. The well-differentiated pleomorphic type occurs in adults and accounts for 5% of the cases. Histologically, small, dark, spindle-shaped cells and small, round, blue cells within a loose myxoid background characterize rhabdomyosarcoma.