Fig. 5

Epidermal inclusion cyst of the axilla. A hypoechoic and rounded formation (white asterisks) can be easily observed originating from the dermis, crossing the dermo-hypodermal interface (green arrowhead) and protruding within the subcutaneous tissue (SUBC) with a typical artifact of posterior acoustic enhancement (white arrow) (A). Of note, using high-frequency probes, the canaliculus (yellow arrowhead) between the cyst (white asterisks) and epidermis (white arrowheads) can be clearly recognized (B). High-sensitivity color Doppler does not show intra-cystic vascular signals but only some small vessels in the surrounding soft tissues (C). The histological examination confirms the presence of the unilocular and spherical cyst (D) lined by a multi-layered epithelium (black arrowheads) and containing laminated keratin (Ker). H&E: hematoxylin & eosin