What is a Trichilemmal Cyst?
A trichilemmal cyst, also known as a pilar cyst, is a common, benign cyst that forms under the skin, usually on the scalp. It arises from the outer root sheath of hair follicles and is filled with keratin, a protein found in hair and skin. These cysts are usually smooth, round, and firm, and can sometimes become swollen or infected.
What Causes Trichilemmal Cysts?
The exact cause is not always clear, but they tend to develop when hair follicle cells multiply abnormally and produce keratin that becomes trapped under the skin. Factors that may contribute include:
- Genetic predisposition, as they sometimes run in families
- Trauma or injury to the scalp
- Blockage of hair follicles
They are more common in middle-aged adults and women.
What Are the Symptoms of a Trichilemmal Cyst?
Symptoms usually include:
- A smooth, firm, round lump under the scalp skin
- The cyst is generally painless but can become tender if inflamed or infected
- It may slowly increase in size over time
- In some cases, the cyst may rupture, causing redness and swelling
Most trichilemmal cysts are harmless and asymptomatic unless irritated.
How is a Trichilemmal Cyst Diagnosed?
Diagnosis is generally based on:
- Physical examination by a doctor, noting the typical location and feel of the cyst
- Ultrasound or imaging if the diagnosis is unclear or to rule out other conditions
- Biopsy or removal of the cyst with histological examination if needed to confirm diagnosis
How is a Trichilemmal Cyst Treated?
Treatment options include:
- Observation if the cyst is small, painless, and not causing problems
- Surgical removal is the most common treatment, especially if the cyst is large, painful, infected, or cosmetically concerning
- Antibiotics if the cyst becomes infected
- Proper wound care after removal to prevent infection
Recurrence is possible but uncommon after complete removal.
Can Trichilemmal Cysts Be Prevented?
There is no guaranteed way to prevent these cysts, but good scalp hygiene and avoiding trauma to the scalp may help reduce risk. Early treatment of scalp infections or injuries may prevent cyst formation.
When Should You See a Doctor?
See a doctor if you notice:
- A new lump on your scalp that grows or changes
- Pain, redness, or swelling around the cyst
- Signs of infection such as warmth, pus, or fever
- Recurring cysts or multiple cysts