Prognostic factors in giant cell tumor of bone. A modified histological grading system useful as a guide to prognosis.

An analysis of 26 patients with giant cell tumor of bone was carried out to determine the clinical and pathological factors affecting the prognosis of the tumor, with a follow-up program of more than 3 years. The physical characteristics of the pathological features were measured objectively using an image analyzer. A significant correlation between the therapeutic procedures and recurrence of the tumor was found, but no pathological variables were significantly correlated. Excision or resection en bloc should be performed for the initial treatment of the tumor. Local recurrence could not be predicted on the basis of histological grading. Stromal cell atypia was significantly correlated with metastasis, but multinucleated giant cells bore no correlation to either recurrence or metastasis. The use of a modified histological grading system based not on variations of the stroma and giant cells but only on the atypia of mononuclear stromal cells, either malignant or classical, is recommended for the clinical assessment of the tumor.