As the role of the radiologist in breast imaging has expanded to include the performance of various interventional procedures, so has the clinical responsibility increased.

The breast interventionalist must have knowledge of the indications and techniques for performing procedures, the selection of the best procedure to manage the patient, and the risks, limitations, and contraindications of each procedure. Prior to undergoing the procedure, the patient should have a thorough imaging assessment, and provide a limited clinical history. Post-procedural assessment does require a review of biopsy results and a determination of recommendations for further management; this may involve a clinical visit with the patient.

The purpose of performing a percutaneous biopsy (rather than an open or excisional biopsy) is to provide a diagnosis using a less invasive and less costly procedure. The selection of patients for percutaneous biopsy must take into consideration the potential management decisions for various histological diagnoses. An important role of percutaneous biopsy is to confirm a benign diagnosis for lesions that are indeterminate by mammography (BIRADS 4) and to avoid surgical biopsy of these lesions.

Percutaneous biopsy is also used to determine whether a highly suspicious lesion (BIRADS 5) is malignant, thus avoiding a two step surgical procedure for diagnosis and treatment. Lesions that are considered benign (likelihood of malignancy less than 2%, BIRADS group 3) are managed with early mammographic follow-up. In general, percutaneous biopsy should not be substituted for early mammographic follow-up, but should be recommended for the evaluation of suspicious lesions. Circumstances in which a BIRADS 3 lesion should be biopsied may include the following: patient anxiety/wish, lack of quality mammographic follow-up (i.e. patient traveling), and planned pregnancy.

A pre-biopsy review of the imaging studies must be performed to determine the best type of biopsy for the patient as well as the type of lesion, form of guidance (stereotactic or sonographic), and the direction of approach for the lesion. Upright and prone table stereotactic units offer different and distinct advantages for various types of patients and lesions. Biopsies are often performed in the decubitus position (Fig. 1). Vasovagal reactions are not a problem on the prone table but may occur infrequently with the upright position. The prone table has a long SID which allows ample space for the biopsy equipment. Upright units do not require the patient to be seated. This is ideal for posterior lesions, for patients who are obese (beyond the weight limit of the table), or who are uncomfortable in the prone position (neck/back problems, recent thoracic/abdominal surgery).

The vast majority of suspicious breast lesions are amenable to percutaneous breast biopsy. However, some lesions may not be suited to stereotactic biopsy. Problematic lesions for stereotactic core biopsy include those that are difficult to target or to visualize, and those that may be problematic for diagnosis.

A particularly difficult lesion to diagnose by core biopsy is a radial scar. The pathologist relies on the distinctive architecture as well as the cellular features to make the diagnosis of radial scar. In addition, radial scars may be associated with areas of atypical hyperplasias or ductal carcinomas in situ. Because of these factors, areas of architectural distortion that might represent radial scars are better suited to excisional biopsy rather than percutaneous biopsy. Lesions that are located very posteriorly in the chest wall are difficult to target. These areas are difficult to place in the field of view for stereotactic biopsy and may be better suited to ultrasound-guided biopsy. The use of add-on stereotactic devices over prone table units often facilitates these biopsies.

Clinical considerations for the selection of patients for percutaneous biopsy include an assessment of factors that might increase the risk of the infrequent, but known, potential complications of bleeding or infection. A pre-biopsy clinical assessment of the patient should be conducted either at the time of scheduling or prior to the procedure. Another important clinical consideration is the compressed breast thickness. In general, a thinly compressed breast (< 25mm thick) is not suited to stereotactic guidance and core biopsy, but may be amenable to ultrasound guided biopsy.

In general, tru-cut automated needles are suitable for biopsy of mass lesions. For microcalcifications, vacuum assisted biopsy devices have been shown to be useful to increase the size of the specimens and the diagnostic yield so that one may differentiate between cases of atypical ductal hyperplasia and ductal carcinoma in situ (Fig. 2). The larger gauge biopsy probes (11g Mammotome or 8g MIBB) allow for clip deployment. This technique is especially useful when very small lesions are biopsied and are no longer mammographically evident following biopsy. In the case of suspicious or malignant diagnoses, excision of the site can be performed by use of the clip as the reference point (Fig. 3 and Fig. 4).

Immediate follow-up of the patient after the procedure includes confirmation of hemostasis and post procedural wound-care instructions. The patient should be made aware of when and how she can expect to receive her biopsy results.

One of the most important components of a percutaneous biopsy is the mammographic and pathological correlation of findings and the plan for management of the patient. The level of suspicion of the mammographic lesion, the accuracy of the targeting of the lesions and the confirmation of microcalcifications in the specimen for calcified lesions must be considered carefully and correlated with the cytology or histology. If the level of mammographic suspicion is very high and the biopsy result is benign, excision of the lesion should be considered.

The final recommendation following biopsy is based on the pathological findings and their concordance with the mammographic findings. Lesions that require excision following core biopsy include:

• carcinoma (for treatment)
• insufficient sample
• possible phylloides tumor
• indeterminate papillary lesion
• atypical ductal and lobular hyperplasia
• radial scar.

Mammographic follow-up for benign lesions at six to twelve months is recommended.