Would a cancerous lymph node go down in size with heat and massage? or would it just continue to grow?

Won't touch it: Only powerful remedies (surgery, radiation, chemotherapy) touch cancer. In fact, even a benign enlarged lymph node from a nearby infammatory process won't get smaller if heated / massaged unless it would have done the same by itself.

Grow: A cancerous node will not go down with massage or heat, however, it may alter your perception of the size of the node. Since the node is palpable, you may wish to discuss having fine needle aspirate done by a pathologist or better yet an open biopsy, for a proper diagnosis.