Differences in sonographic features of ruptured and unruptured epidermal cysts.

Objectives: This study aimed to report the differences in sonographic features of ruptured and unruptured epidermal cysts.

Methods: We reviewed and analyzed the sonographic features of superficial epidermal cysts of in 2 subgroups of 46 patients: 20 with ruptured cysts and 26 with unruptured cysts. All lesions were diagnosed either by excisional biopsy or by debridement biopsy. Sonographic features used in the analysis included tumor size, location, echo texture, pericystic changes, boundary, and shape on gray scale sonography and lesion vascularity on color Doppler sonography. Pathologic examinations were reviewed with emphasis on differences between ruptured and unruptured epidermal cysts.

Results: Unruptured epidermal cysts showed significantly higher frequencies of an oval shape, presence of a halo, well-circumscribed boundaries, and lack of blood flow signals (P < .05). In contrast, ruptured cysts usually had a lobulated shape, a slightly poorly defined or poorly defined boundary, the absence of a halo, and intermediate grades of lesion vascularity. The lesion sizes and sonographic features, including dermal attachment, a hypoechoic echo texture, posterior acoustic enhancement, and the presence of intralesional hyperechoic strips and hypoechoic debris, showed no significant differences between the groups (P > .05). In pathologic studies, acute and chronic inflammatory reactions, more prominent microvessels, and abscess formation in the adjacent stromal tissue, the lesions, or both could be detected in the 20 ruptured epidermal cysts but not in the unruptured cysts.

Conclusions: This research shows that recognition of different sonographic features is helpful for differentiating ruptured and unruptured epidermal cysts.