Pilar (Trichilemmal) Cyst

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Published: February 25, 2017
Last reviewed: March 8, 2017

What is pilar or trichilemmal cyst?

Pilar or trichilemmal cyst is a benign (noncancerous) encapsulated growth that originates from the outer sheath of the hair root [1,3]. It is filled with keratin, which is a protein that normally appears in the hair and skin.

The terms pilar and trichilemmal originate from the Latin pilus and Greek trichos, which both mean hair [1,2]. Other names for pilar cyst include wen and isthmus-catagen cyst [2]. Pilar and epidermoid cysts are commonly, but technically incorrectly, called sebaceous cysts.

Pilar cysts can be acquired or hereditary and tend to run in families [1,3]. They most commonly appear in middle-aged women and less likely in children [1,2,3].

Symptoms

Pilar cysts most commonly develop on the scalp [1,3]. Less common locations include scrotum, face, neck and trunk [3]. They can be single or multiple and appear as painless, firm, smooth and mobile lumps from 5 mm to 5 cm in size, covered by a normal, pink or yellow skin without an opening and with little or no hair [1,2]. When inflamed, they can be painful and covered with red skin. Big cysts tend to burst.

Proliferating trichilemmal cysts grow rapidly and can become as big as 25 centimeters [3,4]. They can ulcerate and damage the nearby tissues. They most commonly appear on the scalp and rarely on the back, chest, armpit, groin, buttocks, thigh, vulva, face and eyelid (Picture 4[5].

Pilar (Trichilemmal) Cysts

Pilar cyst on the scalp Pilar (trichilemmal) cyst on scalp
Picture 1. A pilar cyst on the scalp
(source: DermNetNZ, CC license)
Picture 2. Two pilar cysts on the scalp
(source: DermNetNZ, CC license)
Pilar or trichilemmal cyst Proliferating trichilemmal cyst
Picture 3. A small pilar cyst
(source: Dermatology Atlas)
Picture 4. Proliferating trichilemmal cyst
(source: JCAS)

Differential Diagnosis

Other skin cysts that can be similar to pilar cysts:

Treatment

Pilar cysts can be removed by surgical excision. There are no known methods of prevention or treatment at home [4].


Video 1. A surgical excision of a pilar cyst on the scalp.

Pilar cysts only rarely develop into cancer [3].

  • References

      1. Kapadia A, 2014, Pilar cyst  DermNetNZ
      2. Abreu Valez AM et al, 2011, An inflamed trichilemmal (pilar) cyst: Not so simple?  PubMed Central
      3. Laumann AE, Trichilemmal Cyst (Pilar Cyst), Overview  Emedicine
      4. Laumann AE, Trichilemmal Cyst (Pilar Cyst), Medication  Emedicine
      5. Vatanchi M, Proliferating Pilar Tumor, Overview  Emedicine
      6. Vatanchi M, Proliferating Pilar Tumor, Presentation  Emedicine

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