Breast Cancer Chapter 10
Diagnosing Breast Cancer
If a woman has symptoms of breast cancer (such as a lump), or if a suspicious area is found in an imaging exam, the next step is to physically examine the breasts by noting any changes in their appearance and palpating the breast and the underarm region. A complete physical exam may be done as well. If symptoms or results of these exams suggest cancer might be present, then further tests will be done. (Note: The following diagnostic procedures are common to the US; procedures may vary in other countries.)
Diagnostic Imaging Tests:
Mammograms are mostly used for screening, but they can be used for diagnosis as well. Digital mammograms may be used in some facilities for diagnosis as well as screening.
What Abnormalities Can Mammograms Detect?
The two main abnormalities that mammograms can detect are calcifications (see page 9, Screening) and masses.
A mass is a group of cells clustered together more densely than the surrounding tissue. Masses may be benign or cancerous, or they may prove to be cysts. Cysts are hollow and filled with fluid, but they may appear as masses on a mammogram. To confirm that something that appears as a mass on a mammogram is a cyst, either breast ultrasound or aspiration with a needle is necessary. Cysts are benign and are not associated with cancer.
Masses are evaluated in terms of their size, shape, and margins to determine the likelihood that they are cancerous. Some masses may simply be monitored over a period of years for changes. Other masses require biopsy.
Computer-Aided Detection and Diagnosis (CAD)
In CAD, the computer analyzes a digital image of the breast and puts markers on any areas that seem suspicious in order to bring them to the attention of the radiologist. The image can be from a digital mammogram, or scanned from a film mammogram and converted into a digital image. It's not clear at this time whether CAD actually improves the accuracy of breast cancer detection.
Angiogenesis and Cancer Imaging
Angiogenesis is the process of developing new blood vessels. Angiogenesis is important in the normal development of the embryo and fetus, and it also seems to be important to the growth of tumors. In a complex process, cancerous tumors appear to be able to secrete chemicals that stimulate the formation of new blood vessels in their host tissue. These blood vessels support the formation of the tumor.
Unlike normal blood vessel growth, tumor angiogenesis is a disorganized process. It's characterized by chaotic structure; poorly formed, twisted, and fragile vessels; unstable blood flow; and uneven density.
Because cancer angiogenesis is so distinct from normal angiogenesis, it can be imaged and used to give valuable information about the size, shape, location, and extent of a tumor. Several technologies are useful for imaging tumor angiogenesis, including:
- Dynamic contrast-enhanced MRI (DCE-MRI) uses injected gadolinium, a contrast medium, that passes through the tumor blood vessels and makes them distinctive in the MRI image.
- Doppler ultrasound can detect cancer tumors through the increased, uneven bloodflow to the area due to the greater number and size of vessels. A recent development has been the use of microbubbles as ultrasound contrast agents. These become confined in the tumor blood vessels and allow them to show up clearly in the ultrasound.
- Perfusion CT scans are done with a contrast medium to measure vascular characteristics.
- PET scans can be used to evaluate tumor metabolism and oxygenation, as well as blood flow and volume.
Magnetic Resonance Imaging (MRI)
Although MRIs are done along with mammograms for screening women at high risk, they can also be used to examine suspicious areas found by a mammogram. MRIs are good for examining a possible tumor that is obscured by dense breast tissue or by breast implants. Breast MRI is highly accurate in detecting breast abnormalities and is increasingly accurate in diagnosing breast cancer, especially if MRI is combined with CAD software. If a woman has been diagnosed with breast cancer, MRI can be used to determine the size of the cancer and look for any other cancers in the breast.
Breast ultrasound is generally used to examine a suspicious area found on a mammogram. It can help distinguish between cysts and solid masses, and between benign and solid tumors. Ultrasound is particularly useful for women with dense breasts.
Ductograms, also called galactograms, may be performed if there is suspicious nipple discharge. A thin plastic tube is inserted into the duct opening in the nipple. A small amount of contrast medium is injected. This outlines the shape of the duct in an X-ray image and reveals if there is a mass inside the duct.
Nonimaging Diagnostic Tests:
Biopsy is the only way to definitely confirm or disprove the presence of cancer. In biopsy, samples of the suspicious area are removed and examined under a microscope.
There are several types of biopsy:
- Fine needle aspiration biopsy (FNAB) takes only a small amount of tissue from the suspicious area. The doctor may guide the needle in by feeling the mass, or may use ultrasound or sterotactic needle biopsy. Because the needle used in FNAB is so small, it may miss some cancers.
- Core (large needle) biopsy uses a larger needle (about 1/16- to 1/8-inch in diameter) to remove a small core of tissue from the mass. About 3-5 cores are usually taken.
- Mammotome (vacuum-assisted) biopsy uses a hollow probe inserted in a small incision in the breast to remove a small cylinder of tissue. The sample is suctioned out.
- The advanced breast biopsy instrument (ABBI) uses a probe with a rotating circular knife along with a thin, heated electrical wire to remove a large cylinder of abnormal tissue.
- Surgical (open) biopsy removes all or part of the lump for microscopic examination. If the mass is difficult to locate, the doctor may first use imaging to guide a hollow needle to it and then insert a hooked wire through the needle. The hook attaches to the lump, and the doctor uses the wire as a guide to the abnormal tissue so that he or she can remove it.
- Image-Guided Biopsy.Image-guided biopsy is performed when the lesion is too small to be felt, making it difficult to locate by hand (palpation). Biopsy instruments may be guided using mammography (stereotactic), ultrasound, or MRI guidance.
- Mammography (stereotactic) biopsy. The doctor refers to a map of the breast created from mammograms taken from two different angles. The map helps the physician to guide the biopsy needle into the suspicious area.
- Ultrasound-guided biopsy. This procedure is performed by a radiologist or and sonographer and is done with the patient lying on her back or slightly on her side. A local anesthetic is injected into the breast to numb it. The transducer is pressed to the breast and the suspicious area is located. The biopsy needle (either fine needle, core needle, or Mammotome is inserted in the breast and guided in realtime by watching its movement through the breast on a computer monitor. The tissue sample is taken and the needle is removed. If a surgical biopsy is to be performed, a fine wire may be inserted into the suspicious area as a guide for the surgeon.
- MRI-guided biopsy. Because breast MRI is highly accurate in detecting breast abnormalities, it is particularly useful for the biopsy of suspected tumors. It's generally used when the breast lump can be seen on an MRI but not on ultrasound or mammogram. MRI-guided biopsies are usually performed in traditional, closed MRI units. As in a regular breast MRI, the patient lies on her stomach, with her breasts hanging down into two cushioned recesses. An IV line is inserted so that the contrast agent gadolinium can be injected. The breast is gently squeezed between two compression plates, one of which is marked with a grid configuration. Using the grid, the radiologist determines the location of the lesion and calculates the depth and position of needle placement. A local anesthetic is used to numb the breast. The radiologist removes the tissue sample using fine-needle aspiration, a core needle, or a Mammotome, with the needle guided using realtime MRI images. If a surgical biopsy is to be performed, the radiologist may insert a fine wire into the suspicious area as a guide for the surgeon. The procedure usually takes about 45 minutes.
Grading Breast Cancer
To help determine a patient's prognosis, pathologists assign a histologic grade of from 1 to 3 to the patient's cancer. (Histology is the study of tissues, including cellular structure and function.) This is done by studying cells from the tumor under a microscope to determine three factors:
1. Tubule formation. How many of the cancer cells form tubules (duct structures), as normal breast tissue does?
- >75% = 1 point
- 10-75% = 2 points
- <10% = 3 points
2. Nuclear pleomorphism. Do the tumor nuclei look similar to those in normal breast duct cells, or are they larger, more irregular, and darker?
- Uniform nuclei, similar to normal breast tissue = 1 point
- Moderate nuclear variation = 2 points
- Marked nuclear variation, dark coloration, irregular large nucleoli = 3 points
3. Mitotic activity. How rapidly are the cells dividing? The pathologist counts how many mitotic figures (cell divisions) he or she sees in 10 high-power (400X magnification) fields.
- < 5 mitoses per 10 high-power fields = 1 point
- 5-10 mitoses per 10 high-power fields = 2 points
- >10 mitoses per 10 high-power fields = 3 points
The three scores are added together to get a final grade:
- Final score 3-5 = Grade 1
- Final score 6-7 = Grade 2
- Final score 8-9 = Grade 3
Tumors with low grades tend not to grow very aggressively, whereas tumors with high grades tend to be more aggressive and spread more rapidly.
Patients with low-grade ("well-differentiated") tumors may require no further treatment after the tumor is removed. Patients with moderate- or high-grade ("poorly differentiated") tumors generally receive hormone therapy or chemotherapy.
Hormone Receptor Status Tests
Estrogen and progesterone are hormones that can speed the growth of breast cancer cells. Normal breast cells, and also some cancer cells, have receptors (certain types of protein) on their outside surfaces that can attach to estrogen and progesterone. Biopsied tissue is tested to see if either or both of these receptors are present. Women with hormone-receptive cancers have a better prognosis and respond better to hormone therapy than women without these receptors.
Knowing the HER2 status of a tumor is an important aspect of treatment.
HER2 (also called HER2/neu) is a protein that acts as a receptor for a hormone named human epidermal growth factor. This is a naturally occurring substance that can stimulate cells to divide and grow. HER2 is found on the surface of some breast cancer cells. Certain cancer cells have many more HER2 receptors than others do, and these cancer cells are termed HER2-positive. Human epidermal growth factor attaches to these receptors and causes the cancer cells to multiply rapidly. About 15-20% of women with breast cancer have HER2-positive tumors.
There are two tests for HER2:
- ImmunoHistoChemistry (IHC). IHC testing measures the production of HER2 by the tumor. The test results are ranked as 0-1+ (normal), 2+ (moderate), or 3+ (high, HER2-positive).
- Fluorescence In Situ Hybridization (FISH). FISH testing uses fluorescent probes to measure the amount of the HER2 gene in each cell. The HER2 gene is responsible for the overproduction of the HER2 receptor. If there are more than two copies of the HER2 gene, the cancer is HER2-positive. Results are given as FISH-negative (normal levels of the gene are present) or FISH-positive (excessive amounts of the gene are present, also called gene
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