Jaw bone remodeling at the invasion front of gingival squamous cell carcinomas

Background: It is still unknown how jaw bone remodeling occurs at actual invasion sites of oral squamous cell carcinomas. Since there is no other human carcinomas which make a direct invasion of the bone, gingival carcinomas are valuable examples. Methods: Twelve surgical specimens of gingival squamous cell carcinoma were examined histopathologically and immunohistochemically for remodeling of bone and its surrounding tissue. Results: Three types of bone interfaces with carcinomatous invasion were distinguished. These included areas with bone resorption, smooth bone surface and new bone formation. In the bone-resorption area, numerous osteoclasts were located along the bone surface, which was surrounded by myxoid stroma. The myxoid stroma was characterized by immunopositivity for heparan sulfate proteoglycan (HSPG), abundant vascularity and macrophagic infiltration. In the bone-formation area, rows of osteoblasts were aligned on the bone surface. The stroma around osteoblasts was also HSPG-immunopositive, poor in vascularity but rich in activated fibroblasts. In the smooth-bone area, the stroma showed an organizing phase of granulation tissue with slender fibroblasts and mature collagen fibers but with less vascularity and inflammatory infiltrates. Conclusion: The results indicate that the stromal architecture, especially in terms of its inflammatory cellular, vascular and matrix compositions, is strictly regulated in the timing and site of jaw bone remodeling which is causes by carcinomatous invasion.