Usefulness of strain elastography in the differential diagnosis of ruptured epidermal cyst and superficial abscess

Multimodal Imaging Findings of Intrascrotal Extratesticular Lesions Suggestive of Epidermoid Cysts: A Rare Case Report

Intrascrotal extratesticular epidermoid cysts are rare benign lesions that typically present as slow-growing, painless masses. Accurate and early diagnosis is crucial to differentiate them from malignant lesions and guide appropriate management. In this case, we present the multimodal radiological findings of these cysts, including gray-scale ultrasonography (US), color Doppler US, shear wave elastography (SWE), and magnetic resonance imaging (MRI).

Epidermal Cyst Mimicking Thyroid Cancer Metastasis

ABSTRACT

A 26-year-old woman with pulmonary metastasis of thyroid cancer underwent a total thyroidectomy and cervical lymph node dissection followed by 2 courses of 131I therapy. The posttherapeutic whole-body scan after the second dose of 131I therapy showed diffuse tracer uptake in both lungs. Besides this, there is a local abnormal radiotracer uptake in the left axillary region. SPECT/CT images localized this abnormal radioactivity in a subcutaneous, oval-shaped, approximately 2.2-cm slightly hyperdense lesion, which was pathologically confirmed as an epidermal cyst.

The reproducibility of shear wave and strain elastography in epidermal cyst

Purpose

This study evaluated epidermal cyst elasticity using multiple parameters of strain elastography (SE) and shear wave elastography (SWE) and assessed the reproducibility of each parameter.

Methods

This retrospective study included 73 patients with epidermal cysts who underwent SE and SWE. SE scores were classified as 1-4 according to elasticity. The strain ratio was evaluated using the elasticity ratio of lesions and adjacent subcutaneous fat tissue. For SWE, the shear wave velocity (m/s), elasticity (kPa) according to the Young modulus, velocity ratio, and elasticity ratio were evaluated. All values were measured twice. The reproducibility of SE and SWE measurements was assessed. The relationships among SE and SWE measurements were evaluated.

Results

The strain ratio on SE images showed good reproducibility (intra-class correlation coefficient [ICC]=0.789), and SE scores showed substantial reproducibility (kappa=0.753 and kappa=0.758 for readers 1 and 2, respectively). Moderate reproducibility was found for shear wave velocity and elasticity (ICC=0.750 and ICC=0.648, respectively), as well as for the shear wave velocity of the reference tissue and velocity ratio (ICC=0.747 and ICC=0.713, respectively). All SE scores were positively correlated with the strain ratio (P<0.001). The strain ratio in the second SE session was significantly correlated with the elasticity ratio and velocity ratio in the first SWE session (r=0.245, P=0.037; r=0.243, P=0.038, respectively). Other variables were not correlated.

Conclusion

SE and SWE parameters of epidermal cysts showed moderate to good reproducibility. The strain ratio on SE showed good reproducibility and could provide relatively objective and consistent measurements of epidermal cyst elasticity.