Subcutaneous epidermal inclusion cysts: ultrasound (US) and MR imaging findings.
OBJECTIVE
To describe the characteristic US and MR findings of subcutaneous epidermal inclusion cysts.


METHODS
Seventy-nine patients with subcutaneous epidermal inclusion cysts underwent US (n = 70), MR (n = 7), or both (n = 2). On US, the margin, shape, echogenicity, through-transmission, wall, internal debris and vascularity were evaluated. On MR, the shape, wall, signal intensity, internal debris, and enhancement pattern were evaluated.


RESULTS
On US, characteristic findings were well circumscribed (n = 69, 96%), ovoid-shaped (n = 56, 78%), heterogeneously and mildly echogenic (n = 66, 92%), increased through-transmission (n = 66, 92%) and low echoic rim (n = 48, 67%). Internal debris was seen in 31 cases (43%) and often contained linear echogenic reflections (n = 12, 17%), dark clefts (n = 13, 18%), or a mixture (n = 5, 7%). Most masses showed no Doppler flow (n = 70, 97%). On MR, all cases demonstrated a well-demarcated oval-shaped mass with a surrounding rim. On T1-weighted image (WI), the mass showed slightly high T1 signal in 4/9 (44%) and iso-signal in 5/9 (56%). On T2WI, the mass showed high signal in 6/9 (67%), intermediate in 2/9 (22%), and a target appearance in 1/9 (11%). Internal linear dark T2 signal debris was observed in 4/9 (44%). All lesions showed peripheral rim enhancement without central enhancement.


CONCLUSIONS
On US, subcutaneous epidermal inclusion cysts are usually well-circumscribed, oval-shaped, mildly echogenic masses with occasional linear anechoic and/or echogenic reflections, increased through-transmission, hypoechoic rim and no Doppler flow. On MR, an intermediate to high T2 signal mass with occasional low signal debris and no central enhancement can strengthen the diagnosis.
Department of Radiology and Research Institute, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
Hee Kyung
HK
Kim
Sung Moon
SM
Kim
Sang Hoon
SH
Lee
Judy M
JM
Racadio
Myung Jin
MJ
Shin
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004814:Epidermal Cyst / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D040521:Subcutaneous Tissue; D018615:Ultrasonography, Doppler, Color; D055815:Young Adult