Small glands in your neck, armpits, or groin, called lymph nodes, are part of your immune system. When you’re fighting an infection, they can swell to pea-size lumps or larger. They get smaller as you get better. But tell a doctor if they’re swollen for 2 weeks or more, feel hard, grow fast, are close to your collarbone, or the skin over them is red. These, along with weight loss, night sweats, fever, or fatigue, may be signs of cancer.