Cells at risk for the production of bone tumors in radium exposed individuals: an electron microscope study

The endosteal cells of bone from a 75-yr-old woman who had acquired radium internally, as a consequence of her previous employment as a radium dial painter, are documented here for the first time by electron microscopy. As a result of amputation for a fibrosarcoma in the region of the right knee joint, fresh samples of bone and tumor tissue from the femur were made available. A sample of bone, also obtained at amputation from an unirradiated control patient, age 65, was examined from the same site in the femur. A comparison of the bone-marrow interface from the two patients showed that, unlike the control bone where cells were seen close to bone mineral a fibrotic layer was interposed between the marrow cells and the bone mineral in the bone from the radium case. This layer varied in thickness up to 50 microns and was often acellular, although cell remnants and cells, which appeared viable, were sometimes seen within this layer. It is suggested that irradiation of those cells proliferating within, and at the edge of, this replacement fibrotic layer may be the most important in the induction of bone tumors rather than the original cells lying within the 0-10 microns range from bone mineral which has previously been supposed. The nuclear dimensions of the endosteal bone lining cells and their distance from bone mineral have been measured in the bones from the radium and control cases. These dimensions are important not only in understanding the mechanisms by which bone tumors arise but in developing models of carcinogenic risks of other alpha-particle emitting isotopes such as plutonium.