Shear wave elastography of focal salivary gland lesions: preliminary experience in a routine head and neck US clinic.

OBJECTIVES

To evaluate shear wave elastography (SWE) for focal lesions in major salivary glands.

METHODS

Sixty lesions (49 parotid, 11 submandibular) undergoing routine ultrasound (grey scale and Doppler) also underwent SWE before US-guided needle aspiration for cytology. Quantitative indices of the shear elastic modulus (stiffness) were compared with cytological results.

RESULTS

Fifty-five lesions were benign (21 pleomorphic adenomas, 18 Warthin's tumours; 16 others) and 5 malignant (2 mucoepidermoid carcinomas, 1 myoepithelial carcinoma, 1 B-cell lymphoma, 1 nodal metastasis). Shear modulus of benign lesions, median 18.3 kPa, overlapped appreciably with malignant lesions, median 13.5 kPa. However, 2 mucoepidermoid carcinomas had the highest stiffness values (81.9 kPa, 132.0 kPa). Stiffness of pleomorphic adenomas (median 22.5 kPa) was higher than Warthin's tumours (16.9 kPa) (P = 0.05 Mann-Whitney U-test). The standard deviation of stiffness values within a lesion, used as an indicator of spatial heterogeneity, was highest in mucoepidermoid cancers (median 44.2 kPa), followed by pleomorphic adenomas (median 12.4 kPa) and remaining lesions (medians 1.4-10.3 kPa).

CONCLUSION

This study shows a degree of clustering of SWE indices according to pathology although it appears that SWE has suboptimal performance for ruling out malignancy, thus limiting its use in routine practice.

KEY POINTS

• Shear wave elastography is a feasible technique for focal salivary gland lesions. • Elastographic artefacts aggravated by the regional anatomy may hinder this technique. • Elastographic indices vary according to pathology but there is appreciable overlap. • Overlapping indices for malignant and benign lesions limit its utility. • Pleomorphic adenomas have higher elasticity indices, i.e. are stiffer, than Warthin's tumours.