The reaction of giant cell tumors of bone to transplantation into athymic nude mice: including observations on osteoinduction in the host bed.

Fresh biopsy specimens of three typical human giant cell tumors (GCT) were transplanted into athymic mice. The transplants were encapsulated in a host bed-derived fibrous connective tissue envelope. Multinucleated giant cells and mononucleated tumor cells survived chiefly on the vascularized surfaces of the inside of the envelope. Fibroblasts proliferated and filled the interior of the transplants where vascularization was relatively insufficient. Since mitotic figures were absent in multinucleated cells, the question arises whether only the mononuclear stroma cells are neoplastic in nature. Multinucleated cells occasionally showed endocytosed pyknotic cells, and survived transplantation for as long as 35 days. When the original tumor contained islands of osteoid and bone cells, the transplants induced differentiation of mouse host bed connective tissue into normal new bone, including bone marrow.