What types of biopsy procedures may be performed to evaluate breast lesions?
Fine needle aspiration (FNA) is readily available and needs no special equipment. Overall, it is less traumatic than core biopsy or excisional biopsy. However, as only cells are aspirated, the results may be inconclusive. In addition, it is often difficult to evaluate tumor receptor expression on FNA specimens.
Core needle biopsy is a minimally invasive percutaneous procedure that can be performed under US guidance or stereotactic mammographic guidance. A wide range of needles is available on the market in terms of needle gauge and vacuum versus nonvacuum assistance. Which type of needle is used tends to be based on personal preferences, although stereotactic biopsies are almost always done with vacuum assistance to maximize the retrieval of calcifications. Biopsies performed under US tend to be easier and faster to perform than stereotactic biopsies, partly because of the real-time imaging available with US guidance. At our institution, the stereotactic method is used to biopsy calcifications, although biopsy of solid masses may also be obtained using this method. Percutaneous core biopsies are less expensive, are faster to perform, and are less traumatic than surgical biopsies. The false-negative rates are similar to open biopsies.
There are limitations to performing stereotactic core needle biopsies. Lesions that are in the far posterior breast or behind the nipple may be difficult to access. In addition, the minimum compression thickness of the breast required to perform a stereotactic biopsy is 25 to 30 mm, depending on the needle used.
For both core needle biopsy and FNA, the radiologist reviews the pathology results to confirm that the pathology results are concordant with the imaging findings. If core needle biopsy of a category 5 BI-RADS lesion, or a highly suspicious mass, yields benign pathology results, this may be considered “discordant.” Excisional biopsy may then be needed for further evaluation if there is discordance between the pathology results and the imaging appearance.
Needle localization followed by excisional biopsy has traditionally been the reference standard. The area of concern is localized with mammography on the day of surgery, and then the patient goes to outpatient surgery. To confirm removal of the localized lesion, a specimen radiograph is obtained. At our institution, we image the specimen while the patient is still in the operating room, and the findings are called in to the surgeon.