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%.