Ultrasonographic and strain elastographic features of epidermal cyst according to body location

There are not many studies on the differences of ultrasound (US) findings between epidermal cysts (ECs) located in the trunk and those in the extremities.

To compare the sonographic findings of ECs according to location in the body (trunk vs. extremity) and evaluated the feasibility of strain elastography (SE).

This is a retrospective study of 76 patients with surgically confirmed non-ruptured EC who underwent US including SE. The US analyses included size, shape, ratio of depth to length (DLR), involvement of more than half the dermis, "submarine sign," and SE characters of each lesion. SE findings were assigned into four grades based on elasticity.

The submarine sign was more significantly observed in ECs located in the trunk versus extremities (P value = 0.004 and 0.035, respectively). Truncal lesions were significantly more likely to possess an ovoid shape (P < 0.05) and exhibited higher DLR (P < 0.05). There were more cases with low elasticity according to SE (grade 3 or 4) compared to high elasticity (grade 1 or 2). However, we did not observe significant differences between the two locations (P > 0.05). More-than-half signs also did not exhibit a significant difference (P > 0.05).

The submarine sign, ovoid shape, and tall lesions (higher DLR) are common in the trunk. However, the degree of elasticity and number of more-than-half signs did not differ between the two groups.