Metastatic involvement of the temporal bone by malignant tumors is considered to be rare. The actual incidence of metastatic temporal bone tumors, however, is probably much higher than suggested by reports in the literature. The reason for this is that histologic studies are rarely performed on temporal bones in routine postmortem examinations of patients with possible metastatic disease. Also, in patients with multiple metastatic lesions, otologic complaints and signs may often be overshadowed by other more disabling symptoms.
Twelve temporal bones were histopathologically examined from 6 patients who had metastatic temporal bone disease from various primaries and the results obtained in our present series of 6cases were: 3 cases of hematogenous dissemination from a distant primary (a hepatic cell car-cinoma, a bronchogenic squamous cell carcinoma, and an adenocarcinoma of unknown primary);2 cases of direct invasion from adjacent head and neck tumors (squamous cell carcinomas of the eyelid and hypopharynx); and one case of diffuse metastatic leptomeningeal carcinomatosis (a transitional cell carcinoma of the renal pelvis). Among these, to our knowledge either hepatic cell carcinoma or renal pelvis carcinoma metastatic to the temporal bone has not been reported previously in the world literature.
We reviewed the previously published reports of metastatic temporal bone tumors and found that there were 212 reported cases cited in the literature and that the most common sites of origin in order of frequency were breast, lung, pharynx, kidney, and prostate. Our temporal bone study and literature survey reveal that there are three distinct routes of tumor spread from the primaries to the temporal bone: 1) hematogenous dissemination from a distant primary, 2) direct neoplastic extension from adjacent areas, and 3) diffuse metastatic leptomeningeal carcinomatosis (DMLC).
Our study also indicates that in most cases temporal bone symptoms appeared late in the course of disease, but in some cases the otologic symptoms were an initial sign of tumor, which was particularly conspicuous in the cases of DMLC. In the cases of hematogenous dissemination, the metastatic lesion tends to be overlooked or undiagnosed because occult metastases are relatively common or, when symptomatic, the otologic symptoms often resemble the features charaterized by a severe form of mastoiditis. In the cases of direct neoplastic invasion, on the other hand, recognition of temporal bone involvement is usually simple since the primary disease is quite evident.
Although metastatic temporal bone malignancies are rare, otologist should always be aware of existence of this disease entity in clinical practice. It is expected that, with advances and improve-ments in recent diagnostic imaging technology, earlier diagnosis of these difficult lesions will be possible.