Leukemia is cancer of the white blood cells. White blood cells help your body fight infection. Your blood cells form in your bone marrow. In leukemia, the bone marrow produces abnormal white blood cells. These cells crowd out the healthy blood cells, making it hard for blood to do its work. In chronic lymphocytic leukemia (CLL), there are too many lymphocytes, a type of white blood cell.

CLL is the second most common type of leukemia in adults. It often occurs during or after middle age, and is rare in children.

Usually CLL does not cause any symptoms. If you have symptoms, they may include

• Painless swelling of the lymph nodes in the neck, underarm, stomach, or groin
• Fatigue
• Pain or a feeling of fullness below the ribs
• Fever and infection
• Weight loss

Tests that examine the blood, bone marrow, and lymph nodes diagnose CLL. Your doctor may choose to just monitor you until symptoms appear or change. Treatments include radiation therapy, chemotherapy, surgery to remove the spleen, and targeted therapy. Targeted therapy uses substances that attack cancer cells without harming normal cells.

NIH: National Cancer Institute