Trichilemmal cyst (Pilar cyst)

Trichilemmal cyst, also known as a pilar cyst, is a benign, slow-growing cyst arising from the outer root sheath of the hair follicle. It most commonly occurs on the scalp, where it accounts for the majority of scalp cysts.

Unlike epidermoid cysts, trichilemmal cysts usually lack a central punctum and contain dense keratin. They often occur in multiple family members due to an inherited predisposition.

Pathophysiology (Brief)

Trichilemmal cysts arise from the outer root sheath of hair follicles.

Keratin accumulates within the cyst, resulting in progressive enlargement.

The condition may have an autosomal dominant inheritance pattern in some families.

Signs & Symptoms

Typical lesions include:

• Firm, smooth, rounded cyst

• Slow-growing

• Usually painless

• Mobile beneath the skin

• Usually no central punctum

Common sites:

• Scalp (most common)

Less common sites:

• Neck

• Face

Diagnostic Criteria

Diagnosis is based on:

• Solitary or multiple scalp cysts

• Firm, smooth lesion

• Absence of central punctum

• Characteristic location

Investigations

Diagnosis is usually clinical.

Histopathological examination confirms the diagnosis after excision.

Treatment

Non-pharmacological Treatment

• Observe asymptomatic lesions.

• Avoid repeated trauma.

Surgical treatment

• Complete surgical excision of the cyst.

Complications

• Secondary infection

• Rupture

• Cosmetic concerns

• Recurrence after incomplete excision

Prevention

No proven preventive measures exist.

Patient counselling (Important)

• Trichilemmal cysts are benign.

• They commonly occur on the scalp.

• Complete excision usually cures the condition.

• Recurrence is uncommon after complete removal.