A short-term in vivo model for giant cell tumor of bone

Fresh tumor tissue was obtained from 10 patients and homogenized. The suspension was grafted onto the CAM at day 10 of development. The growth process was monitored by daily observation and photo documentation using in vivo biomicroscopy. After 6 days, samples were fixed and further analyzed using standard histology (hematoxylin and eosin stains), Ki67 staining and fluorescence in situ hybridization (FISH).The suspension of all 10 patients formed solid tumors when grafted on the CAM. In vivo microscopy and standard histology revealed a rich vascularization of the tumors. The tumors were composed of the typical components of GCT, including (CD51+/CD68+) multinucleated giant cells whichwere generally less numerous and contained fewer nuclei than in the original tumors. Ki67 staining revealed a very low proliferation rate. The FISH demonstrated that the tumors were composed of human cells interspersed with chick-derived capillaries.A reliable protocol for grafting of human GCT onto the chick chorio-allantoic membrane is established. This is the first in vivo model for giant cell tumors of bone which opens new perspectives to study this disease and to test new therapeutical agents.Giant cell tumor of bone (GCT) is an aggressive skeletal lesion typically located in the epiphyseal end of a long bone [1-3]. The tumor predominantly occurs in the third and fourth decade of life with a slight predilection for females [3-8].GCT is characterized by locally aggressive growth usually leading to extensive bone destruction [9]. The biological behavior of the tumor is, however unpredictable, and attempts to histologically grade the tumors have failed [10-12]. At the genomic level however recurrent cases are characterized by random individual cell aneusomy, while malignant cases show abnormalities at array CGH level [13].GCT is characterized by the presence of numerous Cathepsin-K producing, CD33 +, CD14 - multinucleated osteoclast-like giant cells and plump spindle-shaped stromal ce