Since IL-2 amplifies and activates lymphokine-activated killer cells, This study retrospectively presents our 12-year’s experience in treating pleural effusion, ascites, and pericardial effusion with interleukin-2 (IL-2) and dexamethasone (DEX) intracavitary injections among pediatric cancer patients. The gene discussed is IL2; the disease is pericardial effusion.