Types of Biopsies
Two general categories of biopsies are used to diagnose breast cancer. These are:
- Needle biopsies, which include core needle biopsy and fine needle aspiration.
- Open biopsies, which include excisional biopsy (including wire localization) and incisional biopsy.
Core Needle Biopsy
Core needle biopsy, or cutting needle biopsy, is a method of procuring tissue samples from the breast using a thin, hollow needle. Palpable lumps can be biopsied in a doctor's office using local anesthetic. Using the fingertips to isolate the lump, the doctor makes a small nick in the skin, inserts a needle, and removes a sample of the tissue from the suspicious area. A pathologist, who microscopically evaluates the breast tissue and/or lymph nodes removed during biopsy or surgery for cancer, then examines the tissue sample.
For nonpalpable areas that cannot be felt to be sampled, the procedure is more involved and will likely be performed in a hospital or outpatient clinic because of the need for special equipment to locate and accurately sample the correct area. An ultrasound or special three-dimensional mammography, called stereotactic mammography is used.
A core needle biopsy using stereotactic mammography entails first placing a woman on her stomach on a mammography table with the affected breast fitted through a hole in the table. The breast is compressed so that it will remain in place to record an accurate image. Calculations are made based on this image, and a biopsy device containing a needle automatically takes a number of tissue samples from the affected area in the breast. Multiple samples increase the chances of an accurate diagnosis. This procedure involves little pain because the device inserts and removes the needle very quickly.
A core needle biopsy using ultrasound entails a women lying on her back and the doctor holding an ultrasound transducer against the breast. The transducer makes an image of the area to be sampled, allowing the doctor to follow the needle as it enters the breast and reaches the abnormal area. The needle is then inserted by hand and a sample of tissue is removed.
The core needle biopsy provides several advantages. It supplies specific information about a tumor, such as whether it is in situ or invasive. It is accurate, quick, relatively inexpensive, only mildly uncomfortable, and does not involve surgery.
There are disadvantages to the core needle biopsy. The most important is that the core needle biopsy can produce false negative results. False negatives may occur if the needle misses the tumor and instead takes a sample of normal tissue. This can impact a woman's chances for long-term survival because the undiagnosed cancer may go untreated. Furthermore, the samples taken may not provide complete information about a tumor; a tumor may be diagnosed as being in situ instead of invasive. Taking multiple tissue samples can help limit this potential problem.
Fine Needle Aspiration (FNA)
Fine needle aspiration (FNA), also known as fine needle biopsy, is a method of procuring cell samples using a very thin needle. Although FNA can be performed on both palpable lumps as well as nonpalpable areas found by mammogram, FNA is recommended only for use on palpable lumps. The key to an accurate diagnosis is the removal of an adequate number of cells from the suspicious area. With nonpalpable lesions, however, FNA can frequently remove insufficient samples of cells, especially compared to core needle biopsy.
For palpable lumps, FNA can be done in a doctor's office. During the procedure, the doctor will locate and isolate the lump with the fingertips, insert a very thin needle attached to a syringe, and draw out (or aspirate) a sample of cells. The needle is so thin that there is little pain, and no anesthetic is needed. The whole procedure takes only a few minutes. Then the sample cells will be sent to a doctor or a cytopathologist who specializes in examining individual cells for a diagnosis.
The advantages of FNA are that it is quick, relatively inexpensive, only mildly uncomfortable, and does not involve surgery. FNA is an excellent method of diagnosing cancer when it is performed on a palpable lump by an experienced doctor and is analyzed by an experienced cytopathologist.
There are several disadvantages to using the FNA procedure. FNA is not recommended for nonpalpable lesions. Even for palpable masses, FNA may not remove enough cells for the cytopathologist to be able to make an accurate diagnosis. In addition, false negatives occur in about 0-4% of FNA procedures performed on palpable lesions (Harris et al. 1997). As a result, a woman having an FNA may need to have a more definitive biopsy, such as a core needle or excisional biopsy, to ensure that the palpable lesion is not cancerous.
Another drawback of FNA is that while it can be used to determine if cells are cancerous, it cannot distinguish in situ cancers from invasive cancers. However, these two types of cancers are generally treated differently via surgery. Finally, FNA requires an experienced breast cytopathologist to accurately analyze the sample of cells, a type of physician that not all hospitals or medical centers will have on staff.
An excisional biopsy is the most accurate method for diagnosing breast cancer. It is also referred to as "lumpectomy" or "partial mastectomy." An excisional biopsy is performed by a surgeon and is generally done under a local anesthetic, meaning that the area to be operated on is desensitized, but the patient remains awake. During the procedure, the surgeon makes an incision in the breast and removes the entire suspicious area and a small amount of surrounding normal tissue. Most women are able to have a biopsy and return home the same day.
Wire Localization for Nonpalpable Lesions
A nonpalpable lesion is difficult to locate during an excisional biopsy. Therefore, a radiologist uses a mammography or ultrasound image for direction and a surgeon inserts a very thin wire into the breast as a guide to identify the breast tissue that requires removal. The surgeon then removes the abnormal tissue. This procedure is called wire localization or needle localization.
Once the nonpalpable mass is removed, the tissue is x-rayed immediately. This allows the surgeon and radiologist to match the suspicious areas on a woman's mammogram with those in the biopsy tissue. If the areas do not match, the surgeon has two options. One option is for the surgeon to make an additional attempt to remove the correct tissue. The other option is to wait and rebiopsy at another time when the area has been targeted a second time using the wire localization technique.
Immediately after the tumor is removed from the breast, a frozen section is usually performed. This process entails freezing a portion of the biopsied tissue and then quickly cutting a thin slice for the pathologist to analyze under the microscope. In the past, if a biopsy came back as positive for cancer, surgical treatment was performed immediately. Currently, biopsies are prior to and separate from the definitive surgery. However, immediate results using frozen sections can help alleviate a woman's anxiety.
A high percentage of false negatives may be produced with frozen sections. Therefore, frozen section results are only preliminary and need to be confirmed by a routine fixed sample, which takes about 2 working days to analyze (Harris et al. 1997).
Excisional Biopsy as a Surgical Treatment
The primary function of an excisional biopsy is to diagnose cancer. However, it can also serve as definitive surgery by removing the cancerous tumor from the breast. Definitive surgery consists of the removal of the entire tumor plus a surrounding amount of normal tissue (a margin) and possibly the axillary lymph nodes.
The pathologist will then inspect the tumor margins. If normal tissue surrounds the entire tumor (which is termed clean or uninvolved or negative margins), the surgery is considered definitive and no additional surgery is needed. If there is insufficient normal tissue surrounding the tumor ("dirty" or involved or positive margins), additional surgery is required to remove the remaining tumor.
The excisional biopsy has many advantages over a needle biopsy. It provides a larger sample size, ensuring far fewer false negative results, and provides accurate information on factors such as tumor size, tumor grade, and the presence of estrogen receptors, all of which are key factors in deciding on a treatment plan.
The excisional biopsy has some disadvantages. It is a far more extensive procedure than a needle biopsy. If a large amount of tissue is removed, the appearance and feel of the breast may also be changed. An excisional biopsy is also expensive and has a longer, more painful recovery period.
Incisional biopsy is a surgical procedure done most often on women with advanced-stage cancer whose tumors are too large to be removed as an initial treatment. Only a portion of the tumor is removed, providing a sufficient amount of tissue to procure information essential for developing a treatment plan.