A newborn boy was found at birth to have a large, firm, violaceous tumor involving his left ear. The tumor involved the entire left ear with extension to the periauricular area. The baby's mother had an uncomplicated prenatal history, a normal ultrasound with no evidence of the tumor at 20 weeks' gestation, normal laboratory values, and a spontaneous vaginal delivery at term. The baby's platelet count was 124,000. The baby was initially referred to dermatology on day 3 of life for evaluation of a...