Doctors use many tests to diagnose cancer and find out if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:
- Age and medical condition
- The type of cancer suspected
- Severity of symptoms
- Previous test results
In addition to a physical examination, the following tests may be used to diagnose metaplastic carcinoma of the breast:
Diagnostic mammography. Diagnostic mammography is similar to screening mammography except that more views (pictures) of the breast are taken, and it is often used when a woman is experiencing signs, such as nipple discharge or a new lump. Diagnostic mammography may also be used if something suspicious is found on a screening mammogram.
Ultrasound. An ultrasound uses high-frequency sound waves to create an image of the breast tissue. An ultrasound may distinguish between a solid mass, which may be cancer, and a fluid-filled cyst, which is usually not cancer.
MRI. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium (a special dye) may be injected into a patient's vein to create a clearer picture.
An MRI may be used once a woman has been diagnosed with cancer to check the other breast for cancer, but the benefit of this is questionable. It may also be used for screening (See Prevention ).
Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. The sample removed from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). A biopsy is specified by the technique and/or size of needle used to collect the tissue sample.
- A fine needle aspiration biopsy (FNAB) uses a small needle to remove a small sample of cells.
- A core needle biopsy uses a larger needle to remove a larger sample of tissue. This is usually the preferred biopsy technique for determining whether a physical exam or imaging finding is cancer. A vacuum-assisted biopsy removes multiple large cores of tissue.
- A surgical biopsy removes the largest amount of tissue. This biopsy may be incisional (removal of part of the lump) or excisional (removal of the entire lump). Because it's best to plan curative surgery after a cancer diagnosis has been made, a surgical biopsy is usually not the recommended approach to determining whether an abnormality is cancerous. If a surgical biopsy confirms cancer, then further surgery is usually required to remove remaining cancer in the breast and evaluate the lymph nodes. Therefore, in order to keep surgery to one operation, it is best when a patient receives a core biopsy to diagnose the cancer, followed by the type of cancer surgery with the best chance at removing all of the disease, as determined by the doctor.
- Image-guided biopsy is used when a distinct lump can't be felt, but an abnormality is seen on a radiologic image, such as a mammogram. During this procedure, a needle is guided to the area of concern with the help of mammography, ultrasound, or MRI. A stereotactic biopsy is performed with mammography guidance. A small metal clip may be put into the breast to mark the site of biopsy, in case the sample tissue proves cancerous and additional surgery is required. An image-guided biopsy can be done using a fine needle, core, or vacuum-assisted biopsy, depending on the amount of tissue being removed.
If cancer is diagnosed, surgery is needed to remove the cancer in the breast and evaluate the lymph nodes for the presence of cancer (discussed in Treatment ). The goal is to achieve clear surgical margins (no cancer cells at the edge of the tissue removed during surgery). If lymph nodes show evidence of cancer, the cancer is called lymph node-positive breast cancer (or node-positive, for short); if the lymph nodes do not show evidence of cancer, the cancer is called lymph node-negative breast cancer (or node-negative, for short). Additional information about lymph node evaluation can be found in Staging .
Testing the tissue
The pathologist tests the tissue from the biopsy and the surgery to help guide treatment decisions. Examination of the tumor under the microscope determines if it is invasive or in situ; ductal, lobular, or metaplastic; grade (how different the cancer cells look from healthy cells); and whether the cancer has spread to the lymph nodes. The margins (edges) of the tumor are also examined.
The doctor may also need to do blood tests to learn more about the cancer.
A serum chemistry panel is frequently done to evaluate blood electrolytes (minerals in your body, such as potassium and calcium) and enzymes (specialized proteins) that can be abnormal if cancer has spread. However, it is important to note that many noncancerous conditions can cause variations in these tests, and they are not specific to cancer.
- Alkaline phosphatase is an enzyme that can be associated with disease that has spread to the liver, bone, or bile ducts.
- Blood calcium levels can be elevated if cancer has spread to the bone.
- Total bilirubin count and the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) evaluate liver function. High levels of any of these substances can indicate liver damage, a signal of possible spread to that organ.
Blood tumor marker tests
A serum tumor marker (also called a biomarker) is a substance found in a person's blood that can be associated with the presence of cancer. An elevated serum tumor marker may indicate an abnormal process in the body, which could be due to cancer or a noncancerous condition. Tumor marker testing is not usually recommended for early-stage breast cancer, but these markers may be useful in the follow-up care of recurrent or metastatic disease. Common tumor marker assays in breast cancer include CA27.29, CA15-3, and CEA. Learn more about tumor markers for breast cancer .
The doctor may order additional tests (depending on the individual's medical history and results of the physical examination) to evaluate the stage of the cancer. Read the Staging  section for more information. These tests are not recommended for all patients.
- A chest x-ray may be used to look for cancer that has spread from the breast to the lung.
- A bone scan may be used to look for spread to the bones. A bone scan uses a radioactive tracer to look at the inside of the bones. The tracer is injected into a patient's vein. It collects in areas of the bone and is detected by a special camera. Healthy bone appears gray to the camera, and areas of injury, such as those caused by cancer, appear dark.
- A computed tomography (CT or CAT) scan may be used to look for distant tumors. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium is injected into a patient's vein to provide better detail.
- A positron emission tomography (PET) scan may be used to determine whether the cancer has spread. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient's body. This substance is absorbed mainly by organs and tissues that produce the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.
To learn more about what to expect during common diagnostic tests, read Cancer.Net: Tests and Procedures .