Pea-Sized Movable Lump on the Scalp: Common Causes and Evaluation

A pea-sized, firm, mobile lump on the scalp is most commonly a sebaceous (epidermoid) cyst—a benign, keratin-filled sac arising from a hair follicle. However, other possibilities exist:

Differential Diagnosis

• Sebaceous cyst: Smooth, round, movable; may have a central punctum. Can become inflamed/infected (red, tender, draining).
• Lipoma: Soft, doughy, mobile fat tumor; usually deeper and larger.
• Dermatofibroma: Firm, button-like, often fixed; may dimple on pinching.
• Pilar (trichilemmal) cyst: Similar to sebaceous cyst but firmer, no punctum; common on scalp.
• Enlarged lymph node: Rubbery, mobile; usually posterior scalp/neck. Suggests infection or malignancy.
• Bone lesion: Hard, fixed to skull; rare but concerning.

When to See a Doctor

• Rapid growth, color change, ulceration
• Pain, redness, warmth (signs of infection)
• Multiple lumps or associated systemic symptoms
• History of skin cancer

Management

Asymptomatic sebaceous/pilar cysts can be monitored. Infected cysts need incision/drainage + antibiotics. Definitive treatment is surgical excision of the cyst wall to prevent recurrence. Lipomas are excised if symptomatic or cosmetic concern. Any suspicious lesion warrants biopsy.