Is ultrasound alone sufficient for imaging superficial lobe benign parotid tumours before surgery?

Ultrasound (US) is a valuable technique for the assessment of salivary gland disease and regional nodes. When used in combination with fine needle aspiration cytology (FNAC) or core biopsy it has a high sensitivity and specificity in the diagnosis of tumours. The role of additional cross-sectional imaging (computed tomography (CT) or magnetic resonance (MR)) to help with the diagnosis of benign parotid tumours is questionable except when there is deep lobe extension or the suggestion of malignancy. We investigated 37 FNAC-confirmed benign parotid tumours in patients who had undergone both US and CT or MRI investigations, to find out whether cross-sectional imaging had provided any further useful diagnostic information before operation. Three patients had bilateral Warthin tumours. Tumours ranged in size from 11 to 45 mm (mean 22). Of the 37 patients 35 (95%) had a clearly delineated mass in the superficial lobe of the parotid on US and no further information was gained from additional CT or MRI. On US 34 patients (92%) had features suggestive of a benign tumour, and three had features suggestive of malignancy but these were found to be benign on FNAC and after operation. CT or MRI confirmed these suspicious findings. In two different patients the deep margin was not visible on US (suggestive of deep lobe extension) and this was confirmed on MRI. The mean time delay between US and CT or MRI was four weeks (range 1-44). These results suggest that additional imaging is not required in most patients with a sonographically and FNAC confirmed benign lesion confined to the superficial lobe of the parotid and confirmed by FNAC or biopsy examination.