The study of giant cell tumors in bone

Twelve samples of giant cell tumor of bone were incubated in the authors' laboratory. The activity of the cells was documented by means of time lapse cinemicrography. The multinuclear giant cells (MGCs) with undegenerating nuclei migrating from the explants had active ameboid movement and continuously changed their shapes. The majority of them kept splitting themselves into smaller MGCs until mononuclear cells formed, which were indistinguishable from the original stromal cells in morphology and could take up tritiated thymidine as shown by autoradiography. This splitting process of MGCs is mainly responsible for their vanishing in culture. The authors believe that an MGC is one of the true neoplastic elements. MGCs are present merely in the form of a syncytium derived from neoplastic stromal cells. In culture, the factors maintaining the syncytium are lost and the process opposite to cell fusion appears. Therefore, from a morphological view, MGCs and neoplastic stromal cells are homologous.