Upper back pain severe at times with spasms.occ.chest and stomach pain too.ekg..chest xray..heart enzymes..labs..negative.still worried.lung cancet?

Could be your: Kidney, pancreas, lungs, spinal nerves, etc... Explore further...Also the tests you went thought are not enough to rule out your potential heart problems. The best option is multifunction cardiogram. http://en.m.wikipedia.org/wiki/multifunction_cardiogram wishing you the best luck!

Unlikely: The chest x-ray would show something in the case of cancer. In middle age back pain is usually related to the spine and muscles. Discuss your concerns with your physician.

Very unlikely: There are many other much more likely causes.