The Diagnostic Performance of Ultrasonography and Computed Tomography in Differentiating Superficial from Deep Lobe Parotid Tumors

Abstract

Objectives

To validate and compare ultrasound (US) versus computed tomography (CT) criteria in the localization of superficial/deep lobe tumors of the parotid gland.

Design and Setting

This was a retrospective study of diagnostic tests performed from January 2008 to June 2017.

Participants

We included adult patients who were referred for a neck ultrasonography examination due to parotid tumors, and who subsequently underwent parotid surgery.

Main outcome measures

We assessed the location of parotid tumors, comparing the minimum fascia–tumor distance (MFTD) criterion on an US with eight CT criteria. We analyzed receiver operating characteristic (ROC) curves of the MFTD for malignant, benign, and all parotid tumors, and compared the accuracy, sensitivity, and specificity of the optimal MFTD with those of CT anatomical criteria.

Results

A total of 166 parotid tumors were included. The mean (SD) MFTD in superficial lobe tumors was significantly shorter than that of deep lobe tumors (1.2 [0.7] vs 2.8 [1.9] mm, effect size: 1.84; 95% CI, 1.27 to 2.41). The areas under the ROC curve were 0.63 for malignant tumors and 0.88 for benign tumors. The optimal MFTD cut point was 2.4 mm for the 154 benign parotid tumors and the accuracy, sensitivity, and specificity were 90%, 80% and 91%, respectively. For the 136 benign parotid tumors that underwent CT examination, three criteria had an accuracy of over 90% (FNline, tMasseter and Conn's arc), but the sensitivities were all below 50%.

Conclusions

MFTD is more feasible for benign tumors than for malignant tumors for the localization of parotid tumors. For benign parotid tumors, US is enough to guide operations.

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