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a closed sac that develops abnormally in some body structure

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/04 08:50:43」(JST)

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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[edit source | edit]

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[edit source | edit]

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[edit source | edit]

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 are usually present on parts of the body with relatively little hair.^[4]

Occasionally, an epidermoid cyst will present with trigeminal neuralgia.

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

Diagnosis[edit source | edit]

Macroscopic appearance of a resected cyst

Histology showing epithelium and lamellated keratin (left)

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 of a cystic lesion lined by cornified epithelium containing lamellated keratin without calcifications. They can also be seen as isointense lesions on MRI or hyperintensities on FLAIR.

Treatment[edit source | edit]

Cysts can be removed by excision.^[6]

Surgical resection appears to be the mainstay of treatment; however, the extent of resection is dictated by adherence of the tumor capsule to the surrounding vital structures.^[7] 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. Patients should be aware this will slow the healing process for a new piercing.

References[edit source | edit]

^ Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0-07-138076-0.
^ James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. ISBN 0-7216-2921-0.
^ "Epidermoid cyst". Retrieved 2007-11-14.
^ "cysts - British Association of Dermatologists". Retrieved 2007-11-14.
^ Jehle KS, Shakir AJ, Sayegh ME (2007). "Squamous cell carcinoma arising in an epidermoid cyst". British journal of hospital medicine (London, England : 2005) 68 (8): 446. PMID 17847698.
^ "Minimal excision technique for removal of an epidermoid cyst". Am Fam Physician 65 (7): 1423–4. 2002. PMID 11996427.
^ Epidermoid Cyst; Frontal Lobe; Case Series

External links[edit source | edit]

DermNet lesions/cysts

UpToDate Contents

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English Journal

Clinicopathological features and surgical treatment of intratarsal keratinous cysts.

Zhang ZD, Li X, Li M, Zhao J, Zhou KJ, Qu J.SourceEye Hospital of Wenzhou Medical College, Wenzhou, Zhejiang, China. zzduan@yeah.net
The American Journal of dermatopathology.Am J Dermatopathol.2013 Feb;35(1):78-82. doi: 10.1097/DAD.0b013e31825d9d0d.
PURPOSE: To explore the clinical and histopathologic features and surgical outcome of intratarsal keratinous cyst (IKC).METHODS: The clinical findings, histopathologic evaluations, and immunohistochemical studies in 15 cases of IKC were investigated, retrospectively.RESULTS: Fifteen patients with an
PMID 22771894

Large Epidermal Cyst of the Clitoris: A Novel Diagnostic Approach to Assist in Surgical Removal.

Johnson LT, Lara-Torre E, Murchison A, Garcia EM.SourceDepartments of Obstetrics and Gynecology, Virginia Tech-Carilion School of Medicine, Roanoke, VA 24016.
Journal of pediatric and adolescent gynecology.J Pediatr Adolesc Gynecol.2013 Jan 18. pii: S1083-3188(12)00240-9. doi: 10.1016/j.jpag.2012.11.005. [Epub ahead of print]
BACKGROUND: Epidermal cysts of the clitoris are uncommon and usually associated with previous trauma. Surgical removal is the preferred treatment with close attention to preserve sensation and vascular supply. The use of an alternative coil during Magnetic Resonance (MR) imaging to visualize the ana
PMID 23337308