Flow and image cytometric DNA analysis in rhabdomyosarcoma

Rhabdomyosarcoma is the most common malignant soft-tissue tumor in childhood, with an overall 3-year disease-free survival of 73%. DNA content is known to correlate with prognosis and therapy response in many cancers. To determine the role of DNA content in rhabdomyosarcoma, 23 tumor samples were studied retrospectively: 18 primary tumors and 5 post-chemotherapy recurrences or specimens obtained at second-look surgeries. The DNA analysis was performed on disaggregated paraffin-embedded tissue nuclei by flow and image cytometry and correlated with the histology and clinical history. Of the primary tumors 4 were diploid, 4 polyploid, and 10 aneuploid (9 with a single aneuploid G0G1 peak and 1 multiploid) by flow cytometry. The concordance rate between flow and image cytometry was 19 of 23 (83%); one case did not have flow cytometry available. Most embryonal rhabdomyosarcomas were aneuploid (10 of 12; 83%), and they had a high incidence of recurrence in Stages III and IV (4 of 12; 33%). Although aneuploidy in pediatric cancers may predict a therapeutic response and good prognosis, this was not supported by our findings in rhabdomyosarcoma. The tumor DNA content correlated with the clinical stage but not with the patient's clinical course or tumor histopathological type. DNA content did not appear to be as important a prognostic tool as tumor stage.