CT and MR of temporal bone malignancies primary and secondary to parotid carcinoma.

PURPOSE To review the CT and MR characteristics of temporal bone malignancy, and to evaluate the relationship between malignancies of the temporal bone and parotid gland. METHODS A group of 15 surgical patients with diagnosis of temporal bone malignancy were retrospectively reviewed. These included 11 cases of primary temporal bone malignancy and four cases of secondary carcinoma of the temporal bone from a primary tumor of the parotid gland. Three primary temporal bone malignancies were recurrences, and two secondary tumors were parotid recurrences. RESULTS Five of the 11 patients with primary temporal bone malignancy had parotid infiltration (45%). All four patients with secondary temporal bone destruction caused by parotid carcinoma had erosion of the mastoid, two with erosion of the external auditory canal, and one of the middle ear. CONCLUSIONS It is important radiographically to recognize the close relationship between malignancies of the temporal bone and parotid gland, because either may secondarily invade the other. Suspicion of malignancy in either the temporal bone or parotid gland necessitates complete imaging of the other structure. Temporal bone or skull base erosion were best seen on CT at bone algorithm. MR with and without infusion provided excellent delineation of soft-tissue tumor margins, muscle infiltration, intracranial extension, and vascular encasement.