Epidermoid cyst

Epidermoid cyst
Classification and external resources
Epidermal Cyst, ear
ICD-10	L72.0
ICD-9	706.2
OMIM	131600
DiseasesDB	29388
eMedicine	derm/860
MeSH	[1]

An epidermoid cyst is a benign cyst usually found on the skin. The cyst develops out of ectodermal tissue. Histologically, it is made of a thin layer of squamous epithelium.

Terminology

Several synonyms exist for epidermoid cysts, including epidermal cyst, epidermal inclusion cyst, infundibular cyst and keratin cyst.^[1]:778[2] "Epidermal inclusion cyst" more specifically refers to implantation of epidermal elements into the dermis. Infundibular cyst refers to the site of origin of the cyst: the infundibular portion of the hair follicle. In fact, the majority of epidermal inclusion cysts originate from the infundibular portion of the hair follicle thus explaining the interchangeable,^[3] yet technically incorrect, use of these two terms.

Causes

Epidermoid cysts commonly result from implantation of epidermis into the dermis, as in trauma or surgery. They can also be caused by a blocked pore adjacent to a body piercing. They are also seen in Gardner's syndrome on the head and neck. They can be infected by bacteria and form a pimple-like shape.

Presentation

The epidermoid cyst may be totally asymptomatic, or it may hurt when touched. It can release pus. It is very common for women on the major or minor labia. In contrast to pilar cysts, epidermoid cysts usually present on parts of the body with relatively little hair.^[4]

Although they are not malignant, there are rare cases of malignant tumors arising from an epidermoid cyst.^[5]

Diagnosis

Epidermoid cysts are usually diagnosed when a person notices a bump on their skin and seeks medical attention. The definitive diagnosis is made after excision by a pathologist based on microscopic appearance. They can also be seen as isointense lesions on MRI or hyperintensities on FLAIR.

Treatment

Cysts can be removed by excision.^[6]

In cases where pus and blood are excreted, (particularly in those caused by body piercings,) hydrogen peroxide gel can be used to dry out the cyst. Be aware that this will slow the healing process for a new piercing.^{[citation needed]}

See also

• Sebaceous cyst (since L72.0 is often mixed up with L72.1)
• Proliferating epidermoid cyst
• Verrucous cyst

References

External links

• DermNet lesions/cysts