The summer after six-year-old Christian completed kindergarten, he started complaining that his ear hurt. His mom, Marisa Garcia, thought it was an ear infection from being in the water during a recent beach trip. At first, she didn’t see anything, but then she noticed a lump behind his left ear.

When his face began to swell and the bump grew larger, his parents took him to the emergency room. On June 14, 2021, doctors found a...