[Histologic grading of chondrosarcoma. A qualitative and quantitative analysis of 74 cases of the Hamburg bone tumor register].

Chondrosarcomas are frequent malignant bone tumors. Aside from different subtypes, such as dedifferentiated, mesenchymal and clear-cell chondrosarcoma, chondrosarcomas (classical chondrosarcoma) show different grades of differentiation. The borderline between chondroma and classical chondrosarcoma is not clearly defined. The same chondrosarcoma can be graded differently at different institutes. Standardized therapy concepts are currently in preparation. As the Hamburg Bone Tumor Registry is often consulted for chondrogenic tumors, the histological criteria are based on a series of 74 chondrosarcomas recorded there. The emphasis has been laid on a classification which can be used in daily routine and which is reproducible and in agreement with the classifications of other international groups. Grade I chondrosarcomas (50%) can be distinguished only by growth criteria. The nuclei are small and show high chromatin density. Grade II chondrosarcomas (42%) have medium-sized, regular nuclei with loose chromatin structure. The chondrocytes of grade III cases (8%) show polymorphic nuclei. Binucleas forms, the number of mitoses and cellularity all show considerable overlap for all three grades. So far there are no immunohistological and molecular biological methods for reliable differentiation. The therapeutic consequences of the classification into grades are thorough curettage, in the case of grade I tumors, or complete resection, for grade II and III cases. The long-term results, however, need to be confirmed by a larger number of cases. From 1991 to 1995 the method was applied and proved to be easily practicable in daily diagnostic routine. Some 104 cases of classical chondrosarcomas (grade I 53%, grade II 39%, grade III 8%) were analyzed. Two pathologists both assigned the same grade in 90% of cases.