Usefulness of ultrasound elastography in differential diagnosis of epidermal cysts and ruptured epidermal cysts.

AIM: To evaluate and compare ultrasound elastography (EUS) findings using strain elastography (SE) and shear wave elastography (SWE) in epidermal cyst and ruptured epidermal cysts, and to assess the intra-observer agreement of each method.

MATERIAL AND

METHODS

This retrospective study included 194 patients with surgically confirmed epidermal cysts who underwent ultrasonography (US), including SE and SWE. SE scores were classified into four grades according to elasticity, and strain ratio was calculated using adjacent subcutaneous fat as reference tissue. SWE parameters included shear wave (SW) velocity (m/s) and elasticity (kPa), velocity ratio, and elasticity ratio. Repeated measurements obtained during the same examination were used to assess intra-observer agreement.

RESULTS

Ruptured epidermal cysts showed significantly lower SW velocity and elasticity values than un-ruptured epidermal cysts on SWE (p<0.001). SE score and strain ratio did not differ significantly between the two groups. The intra-observer agreement of strain ratio was good, while that of SW velocity and elasticity ranged from moderate to good.

CONCLUSION

The intra-observer agreement of both SWE and SE parameters was moderate to good. SWE demonstrated significantly lower value in ruptured epidermal cysts, while SE parameters did not. SWE may therefore be a more useful imaging modality for differentiating epidermal cyst rupture and for treatment planning.