Usefulness of Ultrasonography in Differential Diagnosis between Ruptured and Unruptured Epidermal Cysts

Kim, Sang Tae; Lee, Kang Hoon; Kim, Joon Hee; Han, Sang Hwa; Park, Jong Bin; Suh, Kee Suck; Jang, Min Soo; Kim, Geun Tae

Abstract

BACKGROUND
An epidermal cyst is a common keratin-filled epithelial-lined cyst. The treatment of choice for epidermal cysts is surgical excision. If the cyst becomes ruptured, inflamed, or infected, then incision and drainage together with oral antibiotic therapy or intralesional steroid injection treatment is required. Identification of ruptured and unruptured cysts is important for treatment decisions.
OBJECTIVE
The purpose of this study was to evaluate the usefulness of ultrasonography in the diagnosis of epidermal cysts, and to analyze distinctive features that can differentiate between ruptured and unruptured epidermal cysts.
METHODS
We reviewed the clinical and sonographic features of pathologically confirmed epidermal cysts from 2 subgroups of 66 patients: 30 with unruptured cysts and 36 with ruptured cysts. The sonographic features used in the analysis included tumor size, margin, shape, tumor texture, posterior echo, internal debris, and lesion vascularity on color Doppler sonography.
RESULTS
The mean long diameter of the cysts was 10.95 mm in the unruptured cyst group and 12 mm in the ruptured cyst group. Some sonographic features, including heterogenous and hypoechoic echo texture, posterior echo enhancement, and internal hyperechoic and hypoechoic debris, showed no significant differences between the groups (p>0.05). The unruptured cyst group showed cysts with significantly higher frequencies of a well-circumscribed margin, an ovoid shape, and no vascular flow (p<0.05). In contrast, the ruptured cyst group usually had cysts with a poorly defined or slightly poorly defined margin, an irregular shape, peripheral vascular flow, and mild or moderate flow vascularity.
CONCLUSION
The results of this study indicate that ultrasonography is helpful in differentiating between ruptured and unruptured epidermal cysts.