Head Bumps: Causes, Types, and When to See a Doctor

Scalp and Skull Lesions: Differential Diagnosis

Traumatic / Acute

• Cephalhematoma: Subperiosteal blood, doesn't cross sutures (newborns).
• Subgaleal hematoma: Crosses sutures, fluctuant, dangerous blood loss.
• Contusion/laceration: History of trauma.

Benign Growths

• Sebaceous cyst (epidermoid): Mobile, dome-shaped, central punctum, cheesy keratin. Rupture → inflammation.
• Lipoma: Soft, mobile, subcutaneous, not attached to skin.
• Dermatofibroma: Firm, dimple sign, lower legs more common.
• Pilar cyst (trichilemmal): Scalp, firm, smooth, autosomal dominant.
• Osteoma: Hard, fixed to skull, slow-growing.

Inflammatory / Infectious

• Folliculitis: Pustules at hair follicles; S. aureus, Pseudomonas (hot tub).
• Abscess/furuncle/carbuncle: Tender, fluctuant, purulent.
• Cellulitis: Spreading erythema, warmth, tenderness.
• Tinea capitis: Scaly patches, alopecia, black dots; fungal.
• Impetigo: Honey-crusted lesions; S. aureus/strep.

Neoplastic

• BCC/SCC: Sun-exposed scalp (balding men); pearly, ulcerated, scaly.
• Melanoma: ABCDE, amelanotic variants.
• Merkel cell: Rapidly growing violaceous nodule.
• Metastasis: Scalp = "widow's peak" for visceral mets (lung, breast, kidney, colon).

Congenital / Vascular

• Dermoid cyst (midline, may have sinus tract).
• Hemangioma (infantile, involutes).
• AVM, venous malformation.

When to Biopsy / Refer

• Growing, changing, bleeding, ulcerated.
• Fixed to bone, hard, irregular.
• >1 cm, persistent >4-6 weeks.
• High-risk patient (immunosuppressed, prior skin cancer).
• Dermatology → dermoscopy, biopsy, excision.