Trichilemmal cyst

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Trichilemmal cyst
Other namesWen, pilar cyst, or Isthmus-catagen cyst[1][2]
Trichilemmal cyst: Note the thick, durable, white shell
SpecialtyDermatology Edit this on Wikidata
Relative incidence of cutaneous cysts: Trichilemmal cyst is labeled near top.

A trichilemmal cyst (or pilar cyst) is a common

tumors, also called proliferating trichilemmal cysts, which are benign, but may grow aggressively at the cyst site.[4] Very rarely, trichilemmal cysts can become cancerous.[5]

Classification

Trichilemmal cysts may be classified as sebaceous cysts,[6] although technically speaking are not sebaceous.[7] "True" sebaceous cysts, which originate from sebaceous glands and which contain sebum, are relatively rare and are known as steatocystoma simplex or, if multiple, as steatocystoma multiplex. Medical professionals have suggested that the term "sebaceous cyst" be avoided since it can be misleading.[8]: 31  In practice, however, the term is still often used for epidermoid and pilar cysts.

Pathogenesis

Histopathology of a trichilemmal cyst, from internal (top) to external (bottom):[9]
- Solid eosinophilic-staining keratin.
- Swollen pale keratinocytes, which increase in height closer to the interior.
- Small, cuboidal, dark-staining basal epithelial cells in a palisade arrangement, with no distinct intercellular bridging.
- Fibrous capsule.
There is no granular cell layer (in contrast to an epidermoid cyst).

Trichilemmal cysts are derived from the outer root sheath of the hair follicle. Their origin is currently unknown, but they may be produced by budding from the external root sheath as a genetically determined structural aberration. They arise preferentially in areas of high hair follicle concentrations, so 90% of cases occur on the scalp. They are solitary in 30% and multiple in 70% of cases.[10]

squamous cell carcinoma
may be mistakenly rendered.

Treatment

Minimal excision is appropriate to treat for some trichilemmal cysts, while others require formal surgical excision.[11] [12] 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 one-fourth the diameter of the cyst. The punch biopsy is used to enter the cyst cavity. The contents of the cyst are 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 that have formed a thick enough wall to be easily identified after the sac is emptied. Small cysts have thin walls, so are 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.

See also

References

  1. OCLC 318263086
    .
  2. OCLC 62736861
    .
  3. PMID 9703156
    .
  4. PMID 6268280
    .
  5. PMID 28913304
    .
  6. ^ "Epidermoid and pilar cysts (previously known as sebaceous cysts)". British Association of Dermatologists. Retrieved 2 April 2014.
  7. ^ "Epidermoid and Pilar Cysts (Sebaceous Cysts) - Patient UK". Retrieved 4 March 2013.
  8. ISBN 978-0721690032
    .
  9. ^ Anne Elizabeth Laumann. "Which histologic findings are characteristic of trichilemmal cyst (pilar cyst)?". Medscape. Updated: Jun 11, 2020,
  10. ^ Laumann, Anne Elizabeth (13 September 2017). "Trichilemmal Cyst (Pilar Cyst)". Medscape.
  11. PMID 11996426
    .
  12. PMID 19333649
    .

External links
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