When you undergo a core needle biopsy, the tissue your doctor takes from your body is used for multiple things:
- It’s put in formaldehyde and sent to the hospital’s pathology lab, to be examined under a microscope by a pathologist.  
- Your oncologist or primary care physician may order a portion of your tissue to be used for molecular testing, to determine what kind of cancer you might have.  
- Additional tissue may be wanted to test if your cancer is susceptible to newer drugs with fewer side effects than chemotherapy.  
- But if there isn’t enough tissue to run all these tests, doctors call that Tissue Exhaustion.