It can look like a simple bump or bruise, a complaint of a bellyache or pain in the bones. But it persists.
The symptoms of childhood cancer can seem like ordinary ailments, but when a young boy or girl isn't getting better and there's no reason why, it's time to see a doctor, according to Dr. Teresa York, the University of Maryland Children's Hospital interim division head of pediatric hematology and oncology.
It's estimated that about 11,630 children under the age of 15 will be diagnosed with cancer in the United States this year, according to the American Cancer Society. It's rare, comprising less than 1 percent of cancers diagnosed annually.
"It comes out of nowhere for parents and families," said York, who is also a University of Maryland School of Medicine assistant professor of pediatrics. "It's awful. It's so shocking, and a lot of times that's the hard part of it. "
And because young children can't always express what hurts -- and because kids bleed and bruise just from being kids -- it can be hard to know when it's time to take symptoms seriously.
"In this day and age, we're all working moms," York said, "and you take care of your kids, and you don't run them to the doctor for every little thing they have. If they're not getting better, I would take them in."
That's the best rule of thumb: If symptoms persist without an explanation for their cause, it's important to get the child checked out. However, preventative care appointments play an important role in ensuring a child is healthy because there isn't a catch-all screening for childhood cancer.
"For melanoma, you're checking your moles," York said. "For breast cancer, you're doing your mammogram. There really isn't any screening process for children except their wellness visits."
Due to medical advances, more than 80 percent of children diagnosed with cancer survive five years or more. This is substantially higher than in the mid-1970s when the five-year survival rate was less than 60 percent, according to the American Cancer Society.
And the causes of childhood cancers aren't really known. A small portion of cases can be attributed to causes such as Down Syndrome, and chromosomal and genetic abnormalities.
There are several main types of childhood cancers.