For many families, the day "the world stood still" begins with a symptom as ordinary as a fever. When a child or young adult has a persistent fever, our brains naturally jump to the common cold or the flu. But sometimes, that fever is the body's first "alarm bell" for something much deeper, like leukemia or lymphoma.

Here is why a simple fever can sometimes be the first sign of cancer and the "red flags" that distinguish a normal illness from something serious.

1. Why Cancer Causes a Fever