Epidermal inclusion cyst
Updates to Article Attributes
Epidermal inclusion cysts (also known as a sebaceous cysts) are common cutaneous lesions that represent proliferation of squamous epithelium within a confined space in the dermis or subdermis.
The term sebaceous cyst implies that the lesion originates in the sebaceous glands, which is not correct and as such the term epidermal inclusion cyst is preferred.
Clinical presentation
Epidermal cysts are either found incidentally or present as a firm non-tender lump. If they rupture a local inflammatory response to the necrotic debris released can mimic infection. Although they can be found anywhere, they are typically located on the scalp, face, neck, trunk, and back 1. Rarely they can be seen within bones representing an intraosseous epidermoid cyst (case 11) 2.
Rarely epidermal cysts can undergo malignant degeneration with squamous cell carcinoma 1.
Pathogenesis
The are thought to occur as a result of 1-2:
- traumatic / surgical implantation
- occlusion of the pilosebaceous unit
- congenital rests of cells
- human papillomavirus type 57 or 60 infections implicated palmoplantar epidermoid cysts 1
They are closely related to:
Radiographic features
On all modalities they appear as well circumscribed masses arising in or just deep to the skin.
Ultrasound
Well circumscribed predominantly hypoechoic mass, if small mimics a cyst. Larger masses can be a little heterogeneous.
CT
The density of epidermal inclusion cysts is similar to that of water.
MRI
Imaging on MRI is similar to that of CNS epidermoid cysts or cholesteatomas, namely the content of the cyst is similar to CFS / water.
-
T1:
- lowlow / intermediate -
T2:
- highhigh -
DWI
- some true restricted diffusion (similar to soft tissue on ADC)
- superimposed T2 shine through
-
T1 C+ (Gd)
- no enhancement centrally
- may have thin peripheral enhancement
Complications
- superimposed infection
- rupture
- concurrent occurrence of tumours within them - e.g. melanoma (very rare) 4
Treatment and prognosis
They are benign and generally do not require treatment. If infected they may require incision and drainage. If they continue to grow they may require excision.
Differential diagnosis
General imaging differential considerations include
- ganglion cyst (if near a joint)
- neurogenic tumours e.g. neurofibroma
- nodular fasciitis
- myxoid tumours
- dermatofibrosarcoma protuberans
See also
-<strong>T1</strong> - low / intermediate</li>- +<strong>T1:</strong> low / intermediate</li>
-<strong>T2</strong> - high</li>- +<strong>T2:</strong> high</li>
-</ul><h4>Differential diagnosis</h4><p>General imaging differential considerations include</p><ul>- +</ul><h4>Complications</h4><ul>
- +<li>superimposed infection</li>
- +<li>rupture</li>
- +<li>concurrent occurrence of tumours within them - e.g. melanoma (very rare) <sup>4</sup>
- +</li>
- +</ul><h4>Treatment and prognosis</h4><p>They are benign and generally do not require treatment. If infected they may require incision and drainage. If they continue to grow they may require excision.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include</p><ul>
-</ul><h4>See also</h4><ul><li><a href="/articles/breast-sebaceous-cyst">breast epidermal cyst</a></li></ul>- +</ul><h4>See also</h4><ul>
- +<li><a href="/articles/breast-sebaceous-cyst">breast epidermal cyst</a></li>
- +<li><a href="/articles/epidermoid-cyst">epidermoid cyst</a></li>
- +</ul>
References changed:
- 4. Bajoghli A, Agarwal S, Goldberg L, Mirzabeigi M. Melanoma Arising from an Epidermal Inclusion Cyst. J Am Acad Dermatol. 2013;68(1):e6-7. <a href="https://doi.org/10.1016/j.jaad.2012.04.010">doi:10.1016/j.jaad.2012.04.010</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/23244388">Pubmed</a>
Image ( update )
Image 4 CT (non-contrast) ( update )
Image 14 Ultrasound ( create )
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