Usefulness of cytofluorometric DNA ploidy analysis in distinguishing benign cartilaginous tumors from chondrosarcomas.

In this study, we undertook to prove the usefulness of cytofluorometric DNA ploidy analysis in distinguishing benign cartilaginous tumors from chondrosarcomas. We analyzed the DNA ploidy of 47 cartilaginous tumors using DNA cytofluorometry, which is more sensitive than flow cytometry. All of these tumors were classified into six groups on the basis of clinical, radiologic, and histologic criteria. The 25 tumors in the No. 1 group showed no histologic signs of malignancy regardless of their clinical signs. The four tumors in the No. 2 group showed histologic signs of malignancy, but had benign clinical signs like small bone origin or Ollier's disease. The No. 3 group (13 tumors), No. 4 group (four tumors), and No. 5 group (three tumors) were conventional grade I, II, and III chondrosarcomas, respectively, and the No. 6 group included three dedifferentiated chondrosarcomas. Tumor cells isolated from fresh tumor materials treated with papain and collagenase were smeared on a glass slide and their nuclear DNA was stained with propidium iodide. The DNA content of each cell was measured by a cytofluorometer as fluorescence intensity. The results of this study showed that all of the tumors in the No. 1 group had a diploid pattern with a significantly lower (P<.001) cell proliferative activity than the grade I chondrosarcomas in the No. 3 group, all of which had a diploid pattern. Cytofluorometric analysis also indicated that grade II and III chondrosarcomas in the No. 4 and 5 groups had a higher frequency of hyperdiploid cells (%HDC), including aneuploid and polyploid cells than grade I chondrosarcomas. Importantly, all of the grade I chondrosarcomas showed a %HDC >8%, whereas all of the tumors in the No. 1 and 2 groups showed a %HDC <8%. Therefore, we believe that a %HDC value of 8% is borderline between biologically benign and malignant states in cartilaginous tumors. Four of five patients with aneuploid chondrosarcoma had tumor recurrence and two of these patients died of metastatic disease, although all of the patients except for one with diploid chondrosarcoma were continuously disease free after surgery. Based on these results, we concluded that the data of DNA ploidy analysis, especially cell proliferative activity expressed as %HDC, is more reliable and clinically more useful than the histologic and clinical signs of malignancy in distinguishing benign cartilaginous tumors from chondrosarcomas and even from low grade chondrosarcomas.