Intravascular fibrin thrombi and endothelial cell damage in central giant cell granuloma

Two cases of central giant cell granuloma were studied ultrastructurally. The majority of vessels showed intravascular fibrin thrombi and endothelial cell damage, with gaps in their walls. Plasma, red cells and fibrin were seen subendothelially. The basal lamina was absent from endothelial cells where these components were in contact with their plasma membrane; otherwise it showed multiplication. It is suggested that the absence of basal lamina is the result of degeneration and that these vessels are probably venules and capillaries rather than lymphatics. Myofibroblasts were the dominant stromal cells. Giant cells had little phagocytic activity. It seems that the main function for the stromal cells is the repair of the haematoma and the damaged vessels. It is proposed that the term giant cell reparative granuloma is appropriate, but it should not be used indiscriminately for all jaw lesions containing giant cells.