Reactive changes in the mandible in the presence of squamous cell carcinoma.

A series of 80 mandibles, which were removed as part of composite resections for primary intraoral squamous cell carcinoma, was examined. Of these, 58 were nonirradiated and 22 were previously irradiated. Several changes were observed in the nonirradiated mandible in response to invading tumor. Deposition of new bone was obvious on the periosteal and endosteal surfaces. Osteoclastic resorption of bone was prominent and there was replacement of hemopoietic marrow by fibrous tissue. By contrast, it was found in the irradiated specimens that osteoblastic activity was absent but that osteoclastic activity persisted. The hemopoietic marrow was replaced by fibrous tissue. The lack of osteoblastic activity was interpreted as being due to irradiation. The extent of these changes and their relationship to the invading tumor have implications for both surgeon and pathologist.