Sonographic Diagnosis of Epidermal Inclusion Cysts in the Trunk and Extremities

Hur, Sun Hee; Lee, Min Hee; Hwang, Ji Young

Abstract

PURPOSE: This study was designed to evaluate the sonographic findings of epidermal inclusion cysts in the trunk and extremities and to determine distinguishable features from other soft tissue masses.
MATERIALS AND METHODS
Of 263 soft tissue masses that were evaluated on ultrasound and were surgically confirmed, 27 epidermal inclusion cysts in the trunk and extremities were selected. The anatomic locations were the chest wall (n = 4), abdominal wall (n = 2), buttocks (n = 9) and extremities (n = 12). Two radiologists retrospectively reviewed the sonograms for the following features: location within the superficial tissue, size, margin, echogenicity, internal echotexture with characteristic patterns, presence of posterior enhancement with lateral shadowing and internal vascularity.
RESULTS
All of the masses were located in the subcutaneous layer and had a well-defined margin. The longest diameter of a mass ranged from 0.9-7.4 cm. Of 27 masses, 18 (66.7%) masses were hypoechoic, seven (25.9%) masses were isoechoic and two (7.4%) masses were hyperechoic compared with the surrounding subcutaneous layer. Internal echotexture was heterogeneous in 26 (96.3%) masses and was seen with the following patterns. Hypoechoic/anechoic rod shapes with echogenic fragments were seen in ten masses, focal hypoechoic portions with round to oval shape were seen in four masses, peripheral layering was seen in three masses and only echogenic fragments were seen in two masses. Two lesions had both internal patterns. Posterior enhancement was present in 24 (88.9%) masses and lateral shadowing was present in 21 (77.8%) masses. Twenty-four masses (88.9%) had no vascularity, but three masses showed an increased color signal in the periphery of the masses, which was associated with rupture in two and with infection in one mass.
CONCLUSION
Sonographic diagnosis of an epidermal inclusion cyst may be established when a well-defined, avascular mass with characteristic internal heterogeneity is located in the subcutaneous layer of the trunk and extremities.