Routes of entry of squamous cell carcinoma to the mandible.

A recent preliminary report of a study to determine the patterns of invasion of squamous cell carcinoma to the nonirradiated edentulous mandible indicated that tumor entered mainly through the residual alveolar occlusal ridge. This study has now been extended and includes both nonirradiated and irradiated mandibles. Of a total of 46 nonirradiated mandibles (10 partially dentate and 36 edentulous) invaded by tumor, 41 were invaded through the occlusal surface. This confirms the findings of the preliminary report. These findings indicate that there is a rational basis on pathologic grounds for adopting a conservative approach to the nonirradiated mandible. In 16 irradiated mandibles, the routes of tumor entry were found to be much more variable than in the nonirradiated mandible. In 16 irradiated mandibles, the routes of tumor entry were found to be much more variable than in the nonirradiated mandible, and multiple foci of tumor invasion of the bone were often present wherever tumor in adjacent soft tissues approached the bone. This variability of tumor entry means that a conservative approach to mandibular excision cannot be pursued in the previously irradiated mandible and full-thickness segmental resection is necessary if bone involvement appears likely.