Breast Cancer Diagnosis, Part 1
Mammography is still the gold standard and complements clinical breast exam (the physical exam of the breast done yearly by your doctor), because some breast cancers are felt as a change or abnormality in the breast, while others are diagnosed by mammography alone. Although mammography can pick up better than 90 percent of breast cancers, it has limitations. In women with dense breast tissue, or young or pregnant woman with a prominent glandular pattern, even large, palpable masses can be obscured. In these cases ultrasound can be helpful in detecting tumors that may be cancerous and distinguishing cysts from solid masses. MRI has gradually seen increased use for diagnosing breast cancer. No current criteria have been established for its use, but early reports suggest it may be beneficial in woman with dense breasts or for those who are diagnosed with certain types of breast cancers that tend to involve multiple sites in the same breast.
Biopsy: When a lump can be felt, fine-needle aspiration (FNA) is a simple way of obtaining a tissue specimen because it is a relatively quick outpatient procedure. Usually under x-ray or ultrasound guidance and with local anesthesia, a 22- to 25-gauge needle (approximately 1/32 of an inch) is inserted into the abnormal area and tissue is aspirated into the syringe. A pathologist may be present to examine the aspirated tissue on the spot, and more often than not multiple aspirations are necessary. The disadvantage of this method involves the small amount of tissue obtained, resulting in a higher rate of false negatives then other methods.
A core biopsy uses a similar approach and also is an outpatient procedure. However, instead of a 22-gauge needle, it requires a specialized needle that has a spring-loaded device that extracts a core of tissue. The needle is larger than that used in FNA, approximately 1/16 of an inch, but it yields more tissue and overall, is more accurate than FNA. Core biopsies may be used to diagnose palpable or felt lumps and, under mammographic guidance (stereotactic) or ultrasound guidance, may also be used for abnormalities seen on mammography or ultrasound but that are too small to be felt.
Surgery: Over the past twenty years, there has been a shift from radical breast surgery to minimally invasive approaches to breast cancer treatment. Today, many breast cancers are found through routine yearly screening mammograms and may be too small to feel. In the case of a tumor too small to detect during physical exam, the breast surgeon may use a technique known as needle localization to remove it. In this procedure, a radiologist places guidewires into the breast, guided by mammography images, in order to “localize” the tumor. The patient is then brought to the operating room, where the surgeon follows the guidewire to the exact location of the tumor in order to cut it out (excise it). This insures that the abnormal area is removed, and it has the advantage of allowing the surgeon to go right to the lesion. The abnormal tissue just removed is then x-rayed while the patient is still in the operating room, which is called a specimen mammogram, to verify that the abnormality seen on the original mammogram is actually in the tissue that was surgically removed. If a tumor is large enough to be felt, the surgeon can remove it without using the needle localization technique.
The pathologist carefully examines the tumor specimen under the microscope, a process that usually takes a few days and includes examining the edges, or margins, of the specimen for the presence of cancer cells. Ideally, doctors would like to see a rim of normal tissue removed along with cancer, so that doctors can be sure it is all out. Most surgeons try to balance the removal of enough tissue to achieve negative margins, while leaving as much of the breast intact as possible.
It is difficult to estimate margins at the time of the initial surgery, so it is not uncommon to need additional surgery to achieve wider margins. In addition, the optimal margin size remains controversial. However, if there are cancer cells reaching to the edge of the specimen, this is associated with higher rates of local recurrence, meaning the cancer comes back in the breast. A post-excision mammogram of the breast is another way to check the adequacy of the surgery. Doctors generally do this in cancers that are associated with calcium deposits on the mammogram so that the doctors can see that no abnormal calcifications remain.