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a closed sac that develops abnormally in some body structure

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胞嚢(ほうのう)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/11/09 20:52:32」(JST)

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A trichilemmal cyst, also known as a wen, pilar cyst or isthmus-catagen cyst,^[1]^:779^[2]^:677 is a common cyst that forms from a hair follicle. They are most often found on the scalp. The cysts are smooth, mobile and filled with keratin, a protein component found in hair, nails, and skin. They may or may not be tender. Trichilemmal cysts may run in families. Rarely, these cysts may grow more extensively and form rapidly multiplying trichilemmal tumors, also called proliferating trichilemmal cysts, which are benign but may grow aggressively at the cyst site. Very rarely, trichilemmal cysts can become cancerous.^[3]

Cause

Trichilemmal cysts are derived from the outer root sheath of the hair follicle. Their origin is unknown, but it has been suggested that they are produced by budding from the external root sheath as a genetically determined structural aberration. They arise preferentially in areas of high hair follicle concentrations, therefore, 90% of cases occur on the scalp. They are solitary in 30% of cases and multiple in 70% of cases.^[4]

Histologically, they are lined by stratified squamous epithelium that lacks a granular cell layer and are filled with compact "wet" keratin. Areas consistent with proliferation can be found in some cysts. In rare cases, this leads to formation of a tumor, known as a proliferating trichilemmal cyst. The tumor is clinically benign, although it may display nuclear atypia, dyskeratotic cells, and mitotic figures. These features can be misleading, and a diagnosis of squamous cell carcinoma may be mistakenly rendered.

Treatment

Surgical excision is required to treat a trichilemmal cyst. The method of treatment varies depending on the physician's training. Most physicians perform the procedure under local anesthetic. Others prefer a more conservative approach. This involves the use of a small punch biopsy about 1/4 the diameter of the cyst. The punch biopsy is used to enter the cyst cavity. The content of the cyst is emptied, leaving an empty sac. As the pilar cyst wall is the thickest and most durable of the many varieties of cysts, it can be grabbed with forceps and pulled out of the small incision. This method is best performed on cysts larger than a pea which have formed a thick enough wall to be easily identified after the sac is emptied. Small cysts have walls which are thin, and easily fragmented on traction. This increases the likelihood of cyst recurrence. This method often results in only a small scar, and very little if any bleeding.

References

^ 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.
^ http://www.visualdxhealth.com/adult/pilarCyst.htm
^ http://www.emedicine.com/DERM/topic328.htm

UpToDate Contents

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1. 皮膚の良性病変の概要 overview of benign lesions of the skin
2. 頭皮の発疹を有する患者へのアプローチ approach to the patient with a scalp disorder
3. 皮膚付属器癌 cutaneous adnexal tumors
4. Dissecting cellulitis of the scalp
5. 皮膚石灰沈着症：病院および患者の評価 calcinosis cutis etiology and patient evaluation

English Journal

Osseous metaplasia and mature bone formation with extramedullary hematopoiesis in trichilemmal cyst.

Baldovini C1, Rosini F, Marucci G.
The American Journal of dermatopathology.Am J Dermatopathol.2014 May;36(5):444-6. doi: 10.1097/DAD.0b013e31828a31d5.
PMID 23538899

Trichilemmal cyst of the third fingertip: a case report.

Melikoglu C1, Eren F, Keklik B, Aslan C, Sutcu M, Zeynep Tarini E.
Hand surgery : an international journal devoted to hand and upper limb surgery and related research : journal of the Asia-Pacific Federation of Societies for Surgery of the Hand.Hand Surg.2014;19(1):131-3. doi: 10.1142/S0218810414720113.
INTRODUCTION: Trichilemmal cysts (TCs) are common skin lesions that occur in hairy areas. A TC involving a fingertip has not been previously described in the literature. We herein report a case of a TC occupying a fingertip region.CASE PRESENTATION: A 43-year-old woman presented with a 1.5 × 1.5 cm
PMID 24641757

Japanese Journal

症例報告背部に生じた生じた巨大な増殖性外毛根鞘性囊腫の1例

赤坂英二郎,神可代,北村英夫 [他]
臨床皮膚科 67(7), 507-510, 2013-06
NAID 40019703698

Bacterial pericarditis caused by infected trichilemmal cyst

LODHA Ankur,ENAKPENE Evbu,HARAN Mehandi,SADIQ Adnan,SHANI Jacob
Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy 18(2), 251-254, 2012-04-01
NAID 10030545748

Related Pictures

★リンクテーブル★

リンク元	「毛髪嚢腫」「外毛根鞘嚢腫」
拡張検索	「proliferating trichilemmal cyst」

「毛髪嚢腫」

Trichilemmal cyst
	Classification and external resources
	; Trichilemmal Cyst - Note the thick durable white shell.
ICD-10	L72.1
ICD-9	704.42
ICD-O:	8103/0
DiseasesDB	29388