For core needle biopsy, a biopsy gun is guided to the lesion and fired; the spring-loaded inner needle advances into the lesion and obtains a small core of tissue. - See more at: http://www.healthcommunities.com/cancer-tests/breast-biopsy-...

Preoperative diagnosis of histology and receptor status is important in management of breast cancer. Percutaneous automated core biopsy with biopsy gun (Gun biopsy) was done in fifty patients with palpable breast lump in whom fine needle aspiration cytology (FNAC) was either negative or not done In all patients adequate tissue for histology and receptor status studies was obtained forty-two patients had infiltrating duct carcinoma and eight patients had benign lesions on gun biopsy.
http://www.ncbi.nlm.nih.gov/pubmed/10810554

The titanium Semi-Automatic Biopsy Gun provides a high quality and intact core specimen for histo-pathologic analysis.
http://www.invivocorp.com/Interventional/info.php?id=8

Currently, many surgeons prefer open excision biopsies for palpable lesions (6-8), while US-guided fine-needle aspiration (FNA) biopsies or core biopsies with an automatic biopsy gun are widely used to diagnose non-palpable breast lesions.
http://www.glandsurgery.org/article/view/3687/4713