Why would a doctor want a core needle biopsy? what does this mean they are thinking?

Definitive Diagnosis: In this day and age, we have many noninvasive tests that can get us "in the ballpark" when trying to make a diagnosis. However, when it comes to cancer diagnosis, nothing replaces looking at tissue under the microscope; this requires a biopsy. Thankfully, needle biopsies can usually be done under local anesthesia alone (depending on site) without the need for surgery. Good luck!