Fine Needle Aspiration Biopsy (FNAB)

A fine needle aspiration biopsy, or FNAB, is a test that uses a thin needle to remove fluid or a small amount of tissue from a lump or abnormal area of the breast. This material is then checked for evidence of cancer. The needle can be guided into the area of the breast abnormality while the provider is feeling the lump. If the lump can’t be felt easily, the provider might use an ultrasound or another method called a stereotactic needle biopsy to guide the needle. With ultrasound, the provider can watch the needle on a screen as it moves toward and into the mass.

Once the needle is in place, fluid can be drawn from the cyst or mass, if any is present. Bloody or cloudy fluid can mean either a benign cyst or cancer. If the lump is solid, small tissue fragments can be withdrawn through the needle. Solid lumps can be the result of cancer or of several types of benign breast conditions.

The fluid or tissue drawn by the needle is sent to the lab, placed onto glass slides, and treated with stains to make them more visible under a microscope. Microscopic examination of these samples can often tell whether a breast abnormality is benign or malignant. In other cases, the results of the fine needle aspiration are not definitive, and another type of biopsy is required.