Prognostic relevance of cell biologic and biochemical features in conventional chondrosarcomas

BACKGROUND: Conventional chondrosarcoma is the second most common malignant solid tumor of bone, and its management still poses a challenge for the orthopedic surgeon. Currently, tumor grade is the only parameter of prognostic significance besides stage and, possibly, resection margins. Additional independent prognostic markers therefore would be highly valuable for patient management. METHODS: In the current study, the authors evaluated biologic markers for various chondrocytic phenotypes by histochemical and immunohistochemical technology in a large series of clinically well defined cases of enchondromas and conventional chondrosarcomas, each with at least 5 years of clinical follow-up. RESULTS: The authors' results confirm the strong correlation between clinical behavior and cell differentiation as expressed by marker genes. The phenotypes of the tumor cells are the biologic substrate of the histopathologic appearance of the neoplasms and, thus, the biologic basis for classic tumor grading. Collagen Types II and X, as well as the proteoglycan aggrecan, suggest a mature neoplastic phenotype and good prognosis, i.e., low recurrence rate, rare metastasis, and long survival. Conversely, collagen Type I, together with cell spindling, indicates a transition to a more proliferative, so-called "dedifferentiated" phenotype, which clearly is associated with a poorer prognosis. The changes in cellular phenotypes are accompanied by changes in proliferative activity. Thus, low-grade neoplasms showing mainly mature and terminally differentiated (hypertrophic) chondrocytes display only scant proliferation whereas less differentiated chondrosarcomas with biologically dedifferentiated chondrocytes show significantly higher proliferative activity, a feature that is also highly correlated with prognosis. CONCLUSIONS: These data indicate that molecular markers are to a large extent the biologic basis of the conventional grading, rather than representing independent prognostic markers. The authors' results further indicate that COL1 has significant value in the distinction between enchondromas and low-grade chondrosarcomas including these that are histologically similar. Further understanding of chondrocytic phenotypes will be a promising way to provide new tumor markers for better understanding, diagnosis, and treatment of chondroid neoplasms.