Epidermoid & pilar cysts

Ngā kōmaoa ā-kiri, ā-ruahuru

A cyst is a sac-like pocket of tissue that contains fluid or a semi-solid substance. It is made up of a lining and the contents of the sac.

Epidermoid cysts and pilar cysts (also called sebaceous or trichilemmal cysts) are common. They are non-cancerous (benign), smooth lumps that appear under your skin.

The difference between an epidermoid cyst and a pilar cyst is the lining. The lining of an epidermoid cyst is made up of cells from the outer layers of your skin (the epidermis). The lining of a pilar cyst is made up of cells from hair roots.

Both types of cyst are usually surrounded by a fibrous capsule under your skin. Inside the capsule is a thick, cheese-like substance. This is soggy keratin. Keratin is made up of skin cells and is what hair is made of.

Epidermoid cysts most commonly occur when you are young or middle-aged and men get them more than women.

Pilar cysts occur in middle age and affect women more than men.

Symptoms of epidermoid and pilar cysts

Both epidermoid and pilar cysts are slow growing, smooth, round lumps just under your skin.

Epidermoid cysts can affect any part of your body but mostly appear on your face, neck, chest and upper back. Sometimes they can occur on your scrotum.

Pilar cysts usually appear on your scalp. Sometimes several form on your scalp.

Occasionally either cyst can rupture under your skin and become infected. This makes them red, inflamed and painful.

Diagnosing epidermoid and pilar cysts

If you are concerned about a lump in your skin, have it checked by your general practice team.

Your general practice team can usually diagnose an epidermoid or pilar cyst by examining the lump under your skin. But you may need a biopsy.

Treating epidermoid and pilar cysts

Most cysts do not cause problems, so you do not need any treatment. But if they are causing you problems such as being unsightly or interfering with your everyday life, they can be removed through a minor operation using a local anaesthetic.

If you have an infected cyst, you may need antibiotics and the cyst may need to be drained.

HealthInfo recommends the following pages

DermNet NZ
- Cutaneous cysts and pseudocysts
  An explanation of the different types of cysts, which ones need to be treated, and which ones can be left alone.
- Epidermoid cyst
  Information about epidermoid cysts and how they are treated.
- Trichilemmal cyst
  Information about trichilemmal (pilar) cysts and how they are treated.

Written by HealthInfo clinical advisers. Last reviewed February 2025.

Sources

Page reference: 125440

Review key: HISEC-125440