The invention relates to a method for treating, controlling, or preventing cancerous cell phenotypes and growths in an animal involving the administration of gaseous nitric oxide to one or administration sites in a body. The invention generally is capable of treating cancers found in or on the adrenal gland, bladder, bones, brain, breast, cervix, colon, colorectum, esophagus, gastrointestinal tract, heart, kidney, liver, large intestine, lungs, mouth, ovaries, pancreas, parathyroid, pituitary gland, prostate, salivary gland, skin, small intestine, spleen, stomach, thymus, thyroid, testicles, urinary tract, uterus, vagina, and so forth.