Difference between revisions of "Epidermal inclusion cyst"

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#redirect [[Dermal_cysts#Epidermal_inclusion_cyst]]
'''Epidermal inclusion cyst''', abbreviated '''EIC''', is a very common [[skin pathology]]. It is also know as '''epidermal cyst''', '''epidermoid cyst''',<ref name=Ref_Derm302>{{Ref Derm|302}}</ref> and '''follicular cyst, infundibular type'''.
 
==General==
*Very common.
*The clinical term is ''[[sebaceous cyst]]''.
**This is a misnomer as they contain keratin (not sebum).<ref name=dermis36946>URL: [http://www.dermis.net/dermisroot/en/36946/diagnose.htm http://www.dermis.net/dermisroot/en/36946/diagnose.htm]. Accessed on: 2 November 2012.</ref><ref name=pmid18201468>{{Cite journal  | last1 = Venus | first1 = MR. | last2 = Eltigani | first2 = EA. | last3 = Fagan | first3 = JM. | title = Just another sebaceous cyst? | journal = Ann R Coll Surg Engl | volume = 89 | issue = 6 | pages = W19-21 | month = Sep | year = 2007 | doi = 10.1308/147870807X227791 | PMID = 18201468 | PMC = 2121251 }}.</ref>
**The term may be used to refer to a [[pilar cyst]].
 
==Gross==
Features:<ref>URL: [http://dermatlas.med.jhmi.edu/derm/result.cfm?diagnosis=128 http://dermatlas.med.jhmi.edu/derm/result.cfm?diagnosis=128]. Accessed on: 2 November 2012.</ref>
*[[Nodule]].
*+/-Yellowish colour.
 
DDx:
*[[Pilar cyst]] - indistinguishable on gross.<ref name=dermis36946>URL: [http://www.dermis.net/dermisroot/en/36946/diagnose.htm http://www.dermis.net/dermisroot/en/36946/diagnose.htm]. Accessed on: 2 November 2012.</ref>
*[[Melanoma]].<ref name=pmid18201468/>
 
===Image===
<gallery>
Image:Inflamed_epidermal_inclusion_cyst.jpg |Epidermal inclusion cyst. (WC)
</gallery>
===Microscopic===
Features:
*Cyst lining has a granular layer - '''key feature'''.<ref>URL: [http://emedicine.medscape.com/article/1058907-diagnosis http://emedicine.medscape.com/article/1058907-diagnosis]. Accessed on: 18 March 2011.</ref>
*Trapped collagen bundles at edge of lesion with surrounded by fibroblasts.
*Keratin.
*+/-[[granuloma|Granulomatous inflammation]] due to rupture.
 
DDx:
*[[Pilar cyst]] - no granular layer.
*[[Eccrine hidrocystoma]] - eyelid lesion; same histology.<ref name=pmid10065300>{{Cite journal  | last1 = Adams | first1 = SP. | title = Dermacase. Eccrine hydrocystoma. | journal = Can Fam Physician | volume = 45 | issue =  | pages = 297, 306 | month = Feb | year = 1999 | doi =  | PMID = 10065300 |PMC = 2328272 }}</ref>
*[[Dermoid cyst]] - has adnexal structures, i.e. hair follicle, sebaceous glands, sweat glands.
*Cystic [[squamous cell carcinoma of the skin|squamous cell carcinoma]].<ref name=pmid12079164>{{Cite journal  | last1 = Lin | first1 = CY. | last2 = Jwo | first2 = SC. | title = Squamous cell carcinoma arising in an epidermal inclusion cyst. | journal = Chang Gung Med J | volume = 25 | issue = 4 | pages = 279-82 | month = Apr | year = 2002 | doi =  | PMID = 12079164 }}</ref>
*[[Keratoacanthoma]].<ref name=Ref_Derm302>{{Ref Derm|302}}</ref>
*[[Dermatofibrosarcoma protuberans]] - if lesion is large.
*Hybrid epidermoid and trichilemmal cyst.<ref name=pmid6643785>{{Cite journal  | last1 = Brownstein | first1 = MH. | title = Hybrid cyst: a combined epidermoid and trichilemmal cyst. | journal = J Am Acad Dermatol | volume = 9 | issue = 6 | pages = 872-5 | month = Dec | year = 1983 | doi =  | PMID = 6643785 }}</ref>
 
===Images===
www:
*[http://www.flickr.com/photos/euthman/5517587941/in/photostream/ Epidermal inclusion cyst (flickr.com)].
*[http://www.ajronline.org/content/184/3_supp/S47/F4.expansion.html Epidermal inclusion cyst (ajronline.org)].<ref name=pmid15728019>{{Cite journal  | last1 = Crystal | first1 = P. | last2 = Shaco-Levy | first2 = R. | title = Concentric rings within a breast mass on sonography: lamellated keratin in an epidermal inclusion cyst. | journal = AJR Am J Roentgenol | volume = 184 | issue = 3 Suppl | pages = S47-8 | month = Mar | year = 2005 | doi =  | PMID = 15728019 |URL = http://www.ajronline.org/cgi/pmidlookup?view=long&pmid=15728019}}</ref>
*[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627164/figure/F1/ Ruptured epidermal inclusion cyst (nih.gov)].
 
==Sign out==
<pre>
SKIN CYST, BACK, EXCISION:
- EPIDERMAL INCLUSION CYST.
</pre>
 
===Ruptured===
<pre>
SKIN LESION, RIGHT CHEEK, EXCISION:
- RUPTURED EPIDERMAL INCLUSION CYST.
</pre>
 
===Micro===
The sections show hair-bearing skin with a cyst that is lined by squamous epithelium with a granular layer.  The cyst contains keratin. The overlying epithelium is unremarkable.
 
====Ruptured====
The sections show hair-bearing skin with a cyst that is lined by squamous epithelium with a granular layer. The cyst contains keratin. A mixed inflammatory infiltrate (predominantly lymphocytes and plasma cells) surround the cyst. Neutrophils infiltrate the cyst lining and are admixed with the keratin within its core. 
 
The lesion appears to be completely excised in the plane of section.  Hair follicles are adjacent to the lesion; however, they are not inflamed. The overlying epithelium is unremarkable.
 
====Ruptured without epithelium====
The section shows a dermal collection of neutrophils with acellular keratin-like material surrounded by histiocytes and fibrosis.  The lesion is completely excised in the plane of section.  Hair follicles are adjacent to the abscess; however, they are not inflamed.
 
==See also==
[[Dermal cysts]].
 
==References==
{{Reflist|2}}
 
[[Category:Dermal cysts]]
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