Ultrastructure and histogenesis of peripheral giant cell reparative granuloma of the jaws

Four cases of peripheral giant cell reparative granuloma (PGCRG) of the jaws were studied by electron microscopy to investigate the histogenesis and nature of the basic tissue component and to compare these findings with the ultrastructural features of intra‐osseous benign giant cell tumors of bone. Histologically, the PGCRG of jaw were only found to differ from giant cell tumors by being surfaced by a stratified squamous epithelium and by usually containing dense fibrous connective tissue bands which separated the nodular masses of giant cell tissue and fused with the periosteum of the alveolar bone. Ultrastructurally, the multinucleated giant cells and stromal cells were identical to those found in the benign giant cell tumors of other bones. The multinucleated cells were felt to contain a sufficient number of features in common with osteoclasts to represent a slightly modified form of that cell. The ultrastructure of the stromal cells was compatible with the various stages of differentiating osteoprogenitor cells. The PGCRG is felt to be of osseous origin and to represent the periosteal counterpart of the central giant cell lesions of bone.