Rhabdomyosarcoma in children. Correlation of form and prognosis in one institution's experience.

All cases of rhabdomyosarcoma and undifferentiated sarcoma accessioned at Texas Children's Hospital since 1954 were reviewed. Electron microscopy and immunohistochemistry were used as aids to diagnosis. Rhabdomyosarcoma was diagnosed by study of biopsy specimens obtained prior to therapy in 63 of these 105 cases. Clinical information extending for at least 1 year was available in 47 cases; these cases were used for correlative study. Cellular anaplasia--defined as nuclear enlargement, hyperchromasia, and abnormal mitoses--was noted in 14 cases; 12 of these 14 died an average of 1.53 years after diagnosis. Only 10 of the 33 remaining patients died, including only one of eight with well-differentiated tumors. The mean duration of follow-up for survivors was 4.8 years. By chi-square analysis, the difference in survival between the groups with and without anaplasia was highly significant (p = 0.0009). The relative risk of death within 5 years was 2.48 for the group with anaplasia. Patients with well-differentiated tumors were significantly more likely to survive (p = 0.03). In this study, cellular anaplasia correlated strongly with unfavorable prognosis.