Final answer:
Applying a TENS unit for bone cancer pain leads to nerve stimulation, altering pain signal transmission and endorphin release, rather than causing heat production, vasoconstriction, or muscle relaxation.
Step-by-step explanation:
When a nurse is teaching a client about the use of transcutaneous electrical nerve stimulation (TENS) for the management of bone cancer pain, the nurse should explain that applying a TENS unit to the painful area primarily results in nerve stimulation. The electrical currents produced by the TENS unit are intended to interfere with the transmission of pain signals to the brain and stimulate the release of endorphins, which are the body's natural pain-relieving chemicals. This process can help manage pain by altering the perception of pain in the patient, without producing heat directly or causing vasoconstriction or muscle relaxation as their primary effects.