Scalp Bump: Differential Diagnosis from Cyst to Cancer

A firm, irregular, tender, sometimes itchy scalp bump warrants evaluation. Differential:

Common Benign Lesions

• Pilar (trichilemmal) cyst: Firm, mobile, from hair follicle; common on scalp. May inflame.
• Epidermoid cyst: Keratin-filled, central punctum; can infect.
• Lipoma: Soft, doughy, movable; not typically tender unless compressed.
• Pilomatrixoma: Hard, calcified, from hair matrix; often in children/young adults.

Concerning Lesions

• Squamous cell carcinoma (SCC): Scaly, crusted, ulcerated; sun-exposed areas.
• Basal cell carcinoma: Pearly, telangiectatic, rolled borders.
• Melanoma: ABCDE criteria.
• Merkel cell carcinoma: Rapidly growing, violaceous nodule.

Inflammatory/Infectious

• Folliculitis, abscess, hidradenitis suppurativa
• Dermatofibroma (firm, dimples on pinch)

Next Steps

Dermatology referral. Dermoscopy ± biopsy for diagnosis. Treatment: excision (cysts, tumors), antibiotics (infection), observation (benign stable).