Pilar Cyst

What is Pilar Cyst?

Pilar cyst often called trichilemmal cyst or wens are skin-colored small dome-shaped sac usually present below the skin in the scalp but may appear anywhere on the skin surface. These can be felt and seen easily although benign varying in size from 0.5 cm to 5.0 cm.

Histology

The pilar cyst can be characterized as follows:

  • Stratified squamous epithelium (skin) wall
  • Palisaded outer layer
  • No granular coating on the inner surface
  • Very thick pink keratin

Pathophysiology

Pilar cysts are common along the edge of the hair follicle and are segmented between the insertion of the sebaceous gland duct and erector pili muscle where there is no inner root sheath. The reason behind the absence of granular layer is because the squamous epithelium undergoes rapid keratin formation (‘trichilemmal keratinization’).

Epidemiology

The trichilemmal cyst is common amongst:

  • Race: Does not depend on racial predilection
  • Sex: Predominant more in women than in men
  • Age: Common amongst middle aged people

Causes

  • Skin injury: Injury to the skin can accumulate the keratin at one place and form a cyst
  • Blocked glands: Blockage of sebaceous organ can be a cause
  • Hereditary: Likely to occur due to hereditary problem
  • Cells near the skin surface: Multiply itself if they penetrate deeper into the skin

Symptoms

  • Dome-shaped lump: Increases its size gradually and can be of pea size
  • Irritation: Causes itchiness when rubbed against clothes
  • Red in color: Changes its color from skin color to red when infected and inflamed
  • Hair loss: Area covered with cyst loses hair
  • Pain: Ruptures and causes pain
  • Bad smell: When infected, the pus drains out and produces a foul odor

Diagnosis

  • Biopsy of the Cyst
  • CT Scan

Treatment

The pilar cyst does not require any treatment when small in size, but when infected and doubles in size, it requires surgery. Two procedures to get rid of the cyst:

  • Without cutting and leaving the skin intact (enucleation of the cyst)
  • Making an incision in the cyst and draining out all the keratin and stitching the wound

Prognosis

Trichilemmal cysts can be severe but not doesn’t cause cancer. Its transformation to malignant is a sporadic case, but it can be distant metastases.

References

  • https://www.healthline.com/health/skin-disorders/pilar-cyst#diagnosis5
  • https://emedicine.medscape.com/article/1058907-overview#a2
  • https://healthool.com/pilar-cyst/
  • https://www.dermnetnz.org/topics/pilar-cyst/
  • https://www.healthresource4u.com/pilar-cysts-definition-causes-and-treatment.html
  • https://emedicine.medscape.com/article/1058907-overview#a5
  • https://www.dermnetnz.org/topics/pilar-cyst/

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