5% of all malignancies involve the oral cavity. One percent of these malignancies are secondary to neoplasms that are usually found below the level of the clavicles. As it is widely accepted that the jaws do not contain a lymphatic system, it is believed that metastases there occur via the blood stream, a fact that is supported by the occurrence of metastatic foci in areas where spongiosa and slowing of the circulation favour the entrapment of metastatic emboli. This however does not explain why most of the metastases occur in the lower jaw (and in particular in the premolar-molar area) and not in the maxilla, where the spongiosa is more abundant. Batson's plexus has also been mentioned as a possible route of metastasis to the head and neck, thus explaining why, in some cases of metastases, the lungs are not involved, as the blood has not been filtered through the pulmonary bed before reaching the head and neck.
In our review of the literature we found 422 metastatic lesions in the mouth, jaws and the surrounding tissues in 365 patients equally divided between men and women. 56.5% of the cases were above the age of 50. In 228 cases there were other metastases as well, whereas in 114 cases the only metastasis found was the one under study. In 22% of the cases, the metastatic focus in our area was the first indication of the existence of an undiagnosed primary malignant tumour somewhere else. The lower jaw was involved in 61% of the cases and the maxilla in 24%; however the relationship between the lower and upper gingiva is 5 : 8. One fifth of the reported cases of involvement of the tongue were from autopsies, thus indicating that the tongue is more often involved than is generally accepted, but is not thoroughly investigated. It is also believed that the involvement of the oral and perioral tissues is more frequent than reported, because these tissues are not always included in the metastatic (radiographic) series or the autopsies. 22.5% of the metastases were from the lung, 18% from the breast and 12% from the kidney. After the discovery of the metastasis, in most of the cases either irradiation was used or no treatment was undertaken, thus indicating that following the metastatic spread, there is not very much hope of a cure. In relatively few cases the patients were operated on for the metastatic lesion. Finally, in 45% of the cases, the metastatic focus was discovered within the first year; this percentage becomes quite high, if one considers the number of cases (not accounted for) where the metastatic lesion leads to the discovery of the primary and those where both the primary and secondary foci were diagnosed simultaneously.
