p53 and mdm-2 expression in Rhabdomyosarcoma of childhood and adolescence: clinicopathologic study by the Kiel Pediatric Tumor Registry and the German Cooperative Soft Tissue Sarcoma Study.

Rhabdomyosarcomas (RMS) are the most common malignant soft tissue sarcomas in childhood and adolescence. Despite a large number of publications about this heterogeneous group of tumors, little is known about proliferation, p53 and mdm-2 in relation to histological subtype, clinical parameter, and prognosis of patients. We studied 150 cases of RMS treated in the German Cooperative Soft Tissue Sarcoma Study (CWS) by immunohistochemistry on paraffin-embedded tissue, using antibodies against p53, mdm-2, and Ki-67. The results were correlated with histological subtype, mitotic count, and various clinical parameters. Both p53 and mdm-2 were expressed at low levels and did not show differences between embryonal and alveolar RMS. Tumors of patients with metastatic embryonal RMS showed significantly higher levels of p53 protein than nonmetastatic tumors. This might be a clue to an important role of p53 in metastatic embryonal RMS. Nevertheless, neither p53 nor mdm-2 showed any correlation to prognosis. Proliferation measured by Ki-67 immunostaining (KiS5 antibody) or mitotic count did not show significant differences between embryonal and alveolar RMS. In addition, these parameters did not correlate with response to therapy or prognosis. In conclusion, we could not demonstrate that any of the investigated parameters had an influence on prognosis of RMS. p53 protein overexpression might be a crucial step in metastatic disease for patients with embryonal RMS.