Overview

Sebaceous cysts (more accurately epidermoid or pilar cysts) are common benign slow-growing lumps just below the skin surface, filled with keratin protein. Not dangerous or cancerous but can become infected, inflamed, or cosmetically bothersome. Most common on the face, neck, trunk, and scalp.

Symptoms

• Round smooth lump under skin, usually 1-5cm; skin-coloured or slightly yellow
• Small central punctum (blackhead-like opening) may be visible; usually painless
• If infected: redness, warmth, swelling, tenderness, and pus drainage

Causes & Risk Factors

• Skin surface folds inward trapping keratin; blocked hair follicle or sebaceous duct
• Skin trauma or acne; hereditary conditions (Gardner syndrome — rare)

Complications

• Infection and abscess formation
• Rupture into surrounding tissue causing intense inflammation
• Recurrence after incomplete removal

Diagnosis

Clinical diagnosis by appearance and feel. Ultrasound for deep or uncertain lesions. Biopsy of excised material confirms type.

Treatment

• Small asymptomatic cysts may be left alone
• Infected cysts: incision, drainage, and antibiotics first — excision only after infection resolves
• Complete surgical excision including the cyst sac: definitive treatment preventing recurrence
• Do not squeeze or pop a cyst at home — this spreads infection

Prevention

• Treat acne effectively to reduce cyst formation
• Avoid squeezing or traumatising skin
• Seek early treatment if a cyst becomes inflamed or painful

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