Flow DNA analysis of primary bone tumors. Relationship between cellular DNA content and histopathologic classification.

The cellular DNA content of 15 benign and 34 malignant primary bone tumors was analyzed by means of flow cytophotometry. All benign tumors except one of questionable histologic type exhibited a normal DNA content (diploid), whereas 23 of 34 malignant tumors showed an abnormal DNA content (aneuploid). Closer analysis revealed that all supposedly highly malignant tumors, i.e., 16 osteosarcomas and 1 Ewing sarcoma were aneuploid, while 8 of 13 chondrosarcomas, 2 periosteal osteosarcomas, and 1 of 2 adamantinomas were diploid. Interestingly, these diploid malignant tumors represent tumor entities which are known to include variants of low-grade malignancy. Cell distribution analysis showed that the aneuploid tumors exhibited a higher proportion of S-phase and G2 + M cells than the diploid tumors, indicating differences in proliferative activity. However, no significant difference in this respect could be demonstrated between diploid benign and diploid malignant tumors. The current study clearly shows that flow DNA cytophotometry can be applied to most primary bone tumors despite a substantial content of hard tissue. The results also indicate that DNA determinations as an adjunct to conventional histopathologic assessment may provide objective clinically relevant information with respect to the degree of malignancy. Thus, regardless of histogenetic origin, it appears that benign bone tumors as well as malignant bone tumors of low-grade malignancy in general, are diploid, whereas highly malignant bone tumors in general are aneuploid.