Cephalhematoma
Cephalhematoma is a subperiosteal collection of blood present since birth (usually due to birth trauma). Key distinguishing features: 1) Does not cross suture lines (limited by periosteal attachments), 2) Present since birth but may increase in size initially, 3) Takes weeks to resolve, 4) On X-ray, it appears as a soft tissue swelling with well-defined margins respecting suture lines. Subgaleal hematoma crosses suture lines, caput succedaneum is superficial edema that resolves quickly, and encephalocele is a neural tube defect with brain herniation.