OBJECTIVETo study the clinicopathological, immunohistochemical and electron microscopic characteristics of pediatric rhabdomyosarcomas (RMS).

METHODSOne hundred and forty-five cases of pediatric rhabdomyosarcomas were studied by routine histological, immunohistochemical and electron microscopic studies.

RESULTSThere were 97 male and 48 female patients with ages ranging from 4 months to 13 years and a mean of 4.2 years. The follow-up period of 100 patients was from 1 year to 20 years with a mean of 5 years after diagnosis. All cases were subtyped into the following histological categories: embryonal RMS, botryoid RMS, spindle cell RMS, alveolar RMS and solid RMS. Histopathological subtypes, tumor site and tumor stage correlated significantly with the patients' 5 years survival. The best prognosis was observed in spindle cell and botryoid RMS. Embryonal RMS carried an intermediate prognosis. Patients with alveolar RMS and solid RMS had the worst prognosis. Tumors involving bladder, head and neck carried a favorable clinical outcome. Patients with tumors involving trunk extremities retroperitoneum and pelvis did poorly. Immunohistochemically, all cases were positive for Vimentin. The positive staining rates for desmin, SMA and myoglobin were 78%, 75% and 37%, respectively. All tumors were negative for NSE, CD99 and LCA. Electron microscopy study showed features of myofilament and sarcomere in 10 of 15 cases.

CONCLUSIONSRMS is the most common soft tissue sarcoma of childhood. Immunohistochemistry and electron microscopy are helpful in diagnosis and classification of RMS.