Pre-operative assessment of metastatic parotid tumors.

Metastatic disease to the parotid gland is rare and its diagnosing procedures are not established. We assessed several parameters, including the prior history of malignancy, fine needle aspiration cytology (FNAC) and magnetic resonance (MR) imaging and determined the most useful combinations for diagnosing metastatic parotid tumors. The primary tumors were squamous cell carcinomas of the eyelid, larynx, tonsil and of unknown origin, malignant melanoma of the auricle and small cell lung carcinoma. In three of four patients with parotid lymph node metastasis who underwent MR imaging, rim enhancement of the tumor was observed on gadolinium (Gd)-enhanced fat-suppressed T1-weighted MR images (sensitivity 75%). In the histopathologic examinations, the tumor was encapsulated and massive infiltration of normal lymphocytes was found peripheral to the capsule. These were not seen in the patients with metastasis to the parotid parenchyma via hematogeneous dissemination or with advanced-stage parotid node metastasis. The FNAC diagnosis accorded with the tumor histology in five of six patients (sensitivity 83%). Three of the six patients had a prior history of malignancy in other sites (sensitivity 50%). The triad of FNAC, prior history of malignancy and enhanced MR images was identified as the combination most useful in the diagnosis of metastatic parotid tumors (sensitivity 100%).