Drain pineapple, reserving liquid. Fry pineapple in butter 5 minutes. To pineapple liquid add enough water to make 1 cup. Blend cornstarch into the liquid and add chicken noodle soup. Stir gently to dissolve. Pour soup and pinapple liquid into skillet. Add tuna and simmer over low heat until thickened, about 5 minutes. Stir occasionally to prevent sticking. Before serving blend in soy sauce.