Hyperdiploidy has been associated with an unfavorable histology (anaplastic) in Wilms' tumor and with a better response to chemotherapy in unresectable neuroblastoma. Moreover, DNA-aneuploidy was found in rhabdomyosarcoma (RMS), in contrast to Ewing's sarcoma and primitive neuroectodermal tumor (PNET) in a recent report using a limited number of tumors. The latter was suggested to be an additional criterion in the differential diagnosis of childhood sarcomas. We will analyze the cellular DNA content of 100 tumor samples including RMS, PNET, and Ewing's sarcoma using histologic sections (10 or more per tumor sample) from paraffin blocks. DNA histograms will be used to determine: (1) the number of malignant stem lines in each sample; (2) the DNA index of the stem line(s) (i.e., ratio of the modal Go/G1 channel for tumor cells versus that of normal diploid cells) and (3) the percentages of tumor cells in S phase and G2+M phase. The findings will be compared with the histology of the tumors and the histologic subtypes in the case of RMS (embryonal vs. alveolar, and the newly defined by us histologic subtype with aggressive clinical outcome, the solid variant alveolar RMS). Given the fact that all patients were treated homogeneously according to clinical protocols, meaningful comparisons between DNA-ploidy and clinical outcome or response to treatment will be made as well. The findings will help us draw conclusions as to a possible prognostic or diagnostic role of flow cytometry in this group of pediatric sarcomas.
