Utility of Sonoelastography in Differentiating Ruptured From Unruptured Epidermal Cysts and Implications for Patient Care.

OBJECTIVES

This study aimed to evaluate the correlation of sonoelastographic features between ruptured and unruptured epidermal cysts.

METHODS

We performed a prospective survey of 27 patients with clinically suspected epidermal cysts diagnosed by excisional biopsy with prebiopsy sonography and real-time sonoelastography. We statistically evaluated the correlation between elastographic and histopathologic features. To measure the relative hardness on elastography, the Rinside/Routside ratio was used to show the ratio of the elasticity inside and outside the cyst, where the random value R was defined as the median red pixel intensity/(median red pixel intensity + median green pixel intensity + median blue pixel intensity).

RESULTS

Only 24 of the 27 patients were enrolled. Among the 24 diagnosed epidermal cysts, 13 were unruptured cysts, and 11 were ruptured cysts based on histopathologic examination. There was no correlation between sonographically and histopathologically measured cyst diameters. The Rinside/Routside ratio was significantly higher in unruptured cysts than ruptured cysts (mean ± SD, 1.16 ± 0.15 versus 1.04 ± 0.13; P = .047). All values below the cutoff point were considered to indicate ruptured cysts, and the cutoff value was set to 1.0919, which afforded sensitivity of 83.3% and specificity of 66.7%.

CONCLUSIONS

Real-time sonoelastography is able to detect differences in tissue elasticity between ruptured and unruptured epidermal cysts. This study shows the utility of real-time sonoelastography, which has important implications for treatment planning.