A biopsy (in Greek: βίος life and όψη look/appearance) is a medical test involving the removal of cells or tissues for examination. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. When only a sample of tissue is removed with preservation of the histological architecture of the tissue's cells, the procedure is called an incisional biopsy or core biopsy. When a sample of tissue or fluid is removed with a needle in such a way that cells are removed without preserving the histological architecture of the tissue cells, the procedure is called a needle aspiration biopsy.

Several methods for breast biopsy now exist. The most appropriate method of biopsy for a patient depends upon a variety of factors, including the size, location, appearance and characteristics of the abnormality.

• Fine Needle Aspiration

(FNA) Fine needle aspiration (FNA) is a percutaneous ("through the skin") procedure that uses a fine needle and a syringe to sample fluid from a breast cyst or remove clusters of cells from a solid mass. With FNA, the cellular material taken from the breast is usually sent to the pathology laboratory for analysis. A technique similar to FNA can also be used by the radiologist or surgeon to drain fluid from a benign cyst. This procedure is called cyst aspiration. A Fine Needle Aspiration procedure is generally almost painless and takes only a few minutes to perform.

• Core Needle Biopsy

A core needle biopsy is a procedure that removes small but solid samples of tissue using a hollow "core" needle. For palpable (“able to be felt”) lesions, the physician is fixing the lesion with one hand and performing a freehand needle biopsy with the other. In case of non-palpable lesions stereotactic mammography or ultrasound guidance is used. With stereotactic mammography it is possible to pinpoint the exact location of a mass based on images taken from two different angles of the x-ray machine. With ultrasound, the radiologist or surgeon can watch the needle on the ultrasound monitor to help guide it to the area of concern. The needle used during core needle biopsy is larger than the needle used with FNA. The core biopsy needle also has a special cutting edge allowing removal of a bigger sample of tissue. With Core Needle Biopsy a relatively large sample can be removed through a small single incision in the skin. Typically, the breast area is first locally anesthetized with a small amount of anesthetic fluid. Then, the needle is placed into the breast. As with FNA, the radiologist or surgeon will guide the needle into the area of concern by palpating the lump. If the lesion can’t be felt the core needle biopsy is performed under image-guidance using either stereotactic mammography, ultrasound or even magnetic resonance imaging (MRI). A core needle biopsy procedure takes a few minutes to perform and is almost painless.

• Vacuum Assisted Biopsy

Vacuum Assisted Biopsy is a version of Core Needle Biopsy using a vacuum technique to assist the collection of the tissue sample. The needle normally has a lateral (“from the side”) opening and can be rotated allowing multiple samples to be collected through a single skin incision. The Vacuum Assisted Biopsy procedure is similar to normal Core Needle Biopsy.

• Open Surgical Biopsy

Open Surgical Biopsy means that a large mass or lump is removed during a surgical procedure. Surgical biopsy requires an approximately 3 to 5 centimeters incision and is normally performed in an operating room in sterile conditions. Open surgical biopsy in some cases can be performed with local anesthesia but in most cases general anesthesia may be necessary. Ten years ago, most breast biopsies were open surgical procedures. Today most patients are candidates for less invasive biopsy procedures such as core needle biopsy. Depending on the location of the lesion to be biopsied, a radiologist will often perform needle localization beforehand to guide the surgeon to the site being biopsied.

From http://en.wikipedia.org/wiki/Biopsy