Overview of epidermoid cyst

Abstract

Epidermoid cysts are slow-growing, painless masses that elevate the skin and often have a central punctum that represents the plugged orifice of the pilosebaceous follicle. On ultrasound, they have a round to oval structure, well-circumscribed, avascular mass located in subcutaneous tissue along with phenomena of dorsal acoustic amplification and lateral shadowing. On MRI, they have slightly hypointense signal intensity on T1-weighted and intermediate to high signal on T2-weighted. Restricted diffusion is typical of epidermoid cysts. These signs are useful in the differentiation of epidermal cysts from neoplastic lesions. They need early treatment as they can cause cosmetic and functional impairment.

Keywords: ADC, apparent diffusion coefficient; CT, computed tomography scan; Cutaneous cyst; DWI, diffusion weighted images; Epidermal; Epidermoid; Keratin; MRI, magnetic resonance images; PDW, proton-density weighted; Sebaceous; Skin lesion; T1W, T1-weighted; T2W, T2-weighted.

Fig. 1

(A) Clinical variability of epidermoid cysts. Puncta of epidermoid cysts (arrows) that dark color keratin plug overlying cyst cavity tether the cyst to the overlying epidermis. (B) Intraoperative view and surgical specimen. (C) Photograph of the sectioned surgical specimen shows masses with a fibrous capsule that was composed of a laminated white-yellow paste-like material, typical of keratin. (D) Photomicrograph of pathology shows a solitary epidermoid cyst is appreciated in the dermis. Note the thin squamous epithelium image (arrow) and abundant keratin contents image (arrowhead); Original magnification, ×10; Hematoxylin and Eosin staining. (E) Photomicrograph of pathology shows the contents of the epidermoid cyst consist of laminated orthokeratotic material. Cyst wall lined by keratinizing stratified squamous epithelium image similar to the epidermis (arrow); Original magnification, ×100; Hematoxylin and Eosin staining. (F) Schematic illustration of a segment of skin with epidermoid cyst (asterisk). Note the epidermoid cyst that does bulging skin surface (arrow) (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

Fig. 2

A 34-year-old male with a subcutaneous epidermoid cyst on the left buttock. (A) Ultrasound shows a circumscribed mildly echogenic mass. (B) Histologic examination shows a cystic cavity filled with laminated keratin lined by a stratified squamous epithelium that includes a granular layer.

Fig. 3

(A) A 42-year-old female with an epidermoid cyst on the back with a punctum on the surface (arrowhead). (B) Grayscale ultrasound image shows an oval-shaped hypoechoic structure located in the upper hypodermis and dermis with a central hypoechoic band. Notice the connecting punctum (arrowhead) to the subepidermal region. In spite of the dense and irregular appearance, the posterior acoustic enhancement is conserved (arrows).

Fig. 4

(A) Epidermoid cyst with internal echogenicities in connection with the skin. The outlet of the sebaceous cyst is not visible in this ultrasound image. (B) Ultrasound of the testicular shows a round, well-defined lesion with multiple concentric hyperintense internal layers, resembling an onion skin. Pathology findings confirm an intratesticular epidermoid cyst.

Fig. 5

(A) A 40-year-old male with a large epidermoid cyst on the right thigh with telangiectases on the surface (arrowheads). (B) Grayscale ultrasound image shows a mildly echogenic mass with scattered internal dark clefts (arrows). (C) Color Doppler ultrasound image shows no internal blood vessels.

Fig. 6

A 50-year-old woman with a subcutaneous epidermoid cyst. (A) Grayscale ultrasound image shows well-defined hyperechoic lesion with the hypoechoic central area. (B) Color Doppler ultrasound image shows some peripherals vascularity. The lesion was diagnosed as an epidermoid cyst with inflamed.

Fig. 7

Radiographs of epidermoid cysts. (A) Radiograph shows a soft tissue mass in the forearm of a 5-year-old male (arrow). (B) Sagittal skull radiograph shows a lytic lesion in the frontal skull of a 50-year-old female (arrow). (C) The anteroposterior radiograph of finger shows the osteolytic lesion (arrow). Histopathology confirms as an intraosseous epidermoid cyst.

Fig. 8

A 57-year-old female with a palpable left breast nodule. (A) Mammograms show a rounded nodule in the left breast that is well-defined and adherent to the skin. (B) Ultrasound shows a cystic appearance, with some inner echogenicities debris. Histopathology confirms as an epidermoid cyst.

Fig. 9

(A) Epidermoid cyst in a subcutaneous frontal region with a lower density. (B) Axial head CT image in the soft tissue window showing an osseous destructive lesion in the right frontal calvarium with beveled edges and a soft tissue component. Pathology proved epidermoid cyst in a 6-year-old boy. (C) Axial CT scan showing suprasellar epidermoid cyst with the calcified wall. (D) A bone-destroying epidermoid cyst with sclerotic borders is detected on the lateral wall of the left orbit on axial CT scan image. The lesion mainly located on the greater wing of the sphenoid extends into the zygomatic bone, temporalis fossa, and orbit. (E) A 40-year-old male with an epidermoid cyst in the left knee. Axial CT image in the bone window reveals a mass with the homogeneous density of soft tissue extending into the femur bone. Notice the lesion that causes the femur to have sclerosis. (F) Axial CT image obtained through the chest demonstrates a complex subcutaneous cystic masses of the posterior aspect of the upper back. The mass has coarse regions of calcifications.

Fig. 10

An epidermoid cyst has been confirmed on pathological anatomy in a 55-year-old female. (A) Axial head CT image in the soft tissue window with expansile soft tissue mass in the skull vault. The lesion is the intradiploic location with well-demarcated lysis expanding both the inner and outer tables of the skull and well-defined borders. (B) Sagittal oblique CT 3D reformat image shows scalloped bone margin. (C) Axial non-contrast T1W image shows the lesion with a decreased signal. (D–F) Axial T2W, Flair and T2 Gradient images show the mass with an increased signal. (G–H) DWI shows evidence of restricted diffusion along with the ADC map.

Fig. 11

MRI in a 28-year-old male with a subcutaneous epidermal cyst at behind the leg posterior of the leg. (A) On T1W image displays slightly hypointense signal intensity. (B–C) On T2W and PDW images display intermediate to high signal.

Fig. 12

MRI of epidermoid cysts. Note that the signal of epidermoid cyst in the brain may be different from a subcutaneous. (A) The characteristic appearance of an epidermoid cyst in the cerebellopontine angle. The lesion has a similar signal intensity to cerebrospinal fluid on T2-weighted sequences. The diagnosis is confirmed on DWI which demonstrates very bright signals with intermediate ADC values similar to the brain parenchyma (DWI and ADC are not presented here). (B) Axial T1 and T2-weighted images of the lesion. There is a well-circumscribed, ovoid epidermoid cyst in the subcutaneous location. Its signals are low on T1-weighted and high signal on T2-weighted. (C) MRI in a 15-year-old female with a small size epidermal cyst in the finger. MRI shows a well-defined oval-shaped lesion with slightly high signal intensity on a T1W image and low signal intensity on a T2W image (arrow).

Fig. 13

MRI in a 45-year-old male with a medium-size epidermal cyst at the arm. (A) Axial T1W image shows a well-defined oval-shaped mass with a rather monotonous signal that was hyperintense relative to muscle. (B–C) The lesion shows high signal intensity on axial T2W image without and with fat suppression. Intracyst debris of keratinized material is apparent on MRI.

Fig. 14

Illustration step-by-step of resection of an epidermoid cyst. Note that if the cyst is not inflamed or scarred and does not have a residual punctum on the skin, do a linear incision over the middle. If a punctum or scar is present, a small elliptical incision is advisable.

Fig. 15

Intra operative images of step-by-step of resection of an epidermoid cyst (sebaceouscyst).