Cytophotometric studies of the nuclear DNA content in cartilaginous tumors.

The histopathological differentiation between chondromas and low-grade malignant chondrosarcomas can be difficult. For this reason we studied in 37 different cartilaginous tumors the mitotic index and the Feulgen DNA content using a scanning-integration cytophotometric technique. In 23 chondromas the Feulgen DNA content was diploid and showed a unimodal normal distribution. The number of mitoses was 0--0, 5%. The nuclei of a chondroblastoma were also diploid and the Feulgen DNA content was normally distributed. The mitotic index was 1% and few tetraploid nuclei, which were probably G2 nuclei, were observed. In two chondromyxoid fibromas, the average Feulgen DNA content was diploid and normally distributed. Several tetraploid nuclei were noted. The mitotic index was respectively 0.25% and 1.75%. Recurrence was noted in the first case. The Feulgen DNA content and mitotic index were clearly different in the chondrosarcomas. The distribution of the DNA content was bimodal or unimodal in low-grade chondrosarcomas. The mitotic index was less than 3%. In high-grade malignant chondrosarcomas, the histograms were broad unimodal or aneuploid. The mitotic index was above 5%.