Diagnostics

Disease

Biopsy

General

There are a number of different biopsy techniques available to pathologically assess a breast mass, each with its own advantages and disadvantages.  The appropriate procedure and size of the biopsy is determined on an individual basis, and is based on the index of suspicion for malignancy, patient age, and any coexisting conditions (pregnancy, bleeding diathesis).  For example, a larger biopsy sample often yields greater accuracy and more information than a smaller sample, at the expense of increased invasiveness. 

The most commonly performed biopsy techniques for palpable masses (typically done in a surgeon's office) will be described here.  More advanced techniques for sampling non-palpable masses (i.e. stereotactic guided biopsy), performed by a radiologist, will only be mentioned for completion sake.

Fine Needle Aspiration

Fine needle aspiration (FNA) is the least invasive of the biopsy techniques and is one of the first-line diagnostic procedures in the evaluation of a palpable breast mass.  It is most commonly performed with a 21-gauge needle, although some experienced clinicians can get away with a 23-gauge needle, causing less discomfort and bruising.  The procedure has the capability of being both therapeutic and diagnostic.  The best example of this is during aspiration of a cyst.  Aspirate from a cystic lesion is often green tinged and serous (diagnostic), and aspiration should collapse the cystic cavity (therapeutic).  For solid masses, aspiration can be used diagnostically to collect samples for cytologic evaluation.

Clearly every palpable mass should be (at least) considered for FNA, to diagnose and treat cysts and to collect aspirate for cytologic evaluation.  It must also be bore in mind, however, that although FNA has a very low false-positive rate (<1%), the false-negative rate may be as high as 15-20%.  The persistence of a mass, recurrence following repeat aspiration, or one which yields bloody fluid, are all indications for open biopsy.

Core Needle Biopsy

Core needle biopsy (CNB) (aka true-cut or wide-bore needle biopsy) is similar to fine needle aspiration, but allows for larger core sample sizes (particularly useful for solid masses).  Here, a wide, 14-gauge needle is used, and typically is attached to a spring-loaded injection device.  With local anesthetic given, the procedure is often less painful than FNA, despite the wider-bore needle used.

The samples obtained with CNB are often large enough to allow detailed histologic and architectural information, including the type and grade of the tumor, its invasiveness, as well as hormone receptor status.  This is an advantage over FNA, particularly with patients who have large masses suggestive of cancer. 

Excisional Biopsy

The most invasive form of biopsy is the open or excisional biopsy, and is typically reserved for lesions for which some doubt still remains after lesser invasive approaches have been tried, or when a patient wants a benign mass removed.  It is usually performed under general anesthesia, and involves skin incision with removal of the mass, along with breast tissue.  Typically, at least a 1-cm margin of normal breast tissue is excised with the mass, satisfying a lumpectomy for lesions suspicious of cancer.  For benign lesions, only minimal margins are necessary, and in fact, fibroadenomas can literally be "shelled out" of the surrounding breast tissue.

Sentinel Node Biopsy

The sentinel lymph node is the first draining axillary lymph node from the breast. It is thought that by detecting the presence or absence of tumor in this (sentinel) node, one can predict the status of the axilla and potentially avoid the additional morbidity of an axillary node dissection.  Isosulfan blue dye or radiolabeled colloid can be injected into the primary tumor and used to localize the first draining lymph node, during dissection. The sentinel node can be identified by its blue color (since it takes up the dye) or by the use of a Geiger counter (if a radiolabeled colloid is used). The technique is associated with a significant learning curve, but in appropriate hands, it can be a highly effective tool in the staging and management of breast cancer.

Advanced Techniques

When a breast mass is seen on mammogram or by ultrasound, but is too deep or small to be palpated by the physician, a stereotactic guided breast biopsy (aka mammotome) is often useful.  Stereotactic literally means precise location in space and the technique can be applied to fine needle aspirations and core needle biopsies alike.  The procedure was developed as an alternative to open (surgical) breast biopsy, and has the advantage of being minimally invasive and highly accurate.  In this technique, the patient lies fixed on a table and images of the breast are obtained at different angles to triangulate the exact coordinates of the breast abnormality.  Once identified, a needle (mammotome) is introduced into the lesion at the precise coordinates, removing a sample for biopsy.  An additional benefit is that small surgical clips can be introduced through the mammotome to mark the exact location of the lesion, so that later, if open excision is required, the spot can be found quite readily.