Core-needle biopsy 

In this technique, the needle is much thicker and hollow (2-3 millimeters of diameter) so to remove a small cylinder of tumor tissue to be analyzed under the microscope by a pathologist. The procedure is done under local anesthesia and can be guided by ultrasound or mammogram. 

A small cut with a scalpel is done first to help the needle insertion. The syringe is connected to a device that quickly collects a small sample of tissue.

In total, 5-10 tissue samples are extracted that will be conserved in formaldehyde until analyzed under the microscope by a pathologist. 

In pathological sub-classifications you can learn more about the tests done on tumors from cytology or biopsy.