- Doctors use many tests and procedures to diagnose cancer.
- Some tests also determine the stage of cancer (way of describing the cancer, such as where it is located, if or where it has spread, and whether it is affecting the function of other organs in the body), and others help the doctors decide on a treatment plan.
- The most common types of tests used are biopsy, imaging tests, endoscopic tests, and laboratory tests.
The most common diagnostic tests are described below. When choosing a diagnostic test(s), your doctor will consider the person’s age and medical condition, the type of cancer suspected, the severity of the symptoms, and previous test results. Learn more about diagnostic tests for a specific type of cancer. And, not everyone will need all available tests. Learn more about specific tests and procedures that are commonly used in cancer care but should be questioned in specific situations.
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 for most types of cancer, only a biopsy can make a definite diagnosis. A pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease) analyzes the sample that was removed during the biopsy. There are different types of biopsies.
Fine needle aspiration biopsy. This test uses a thin, hollow needle attached to a syringe to collect a small amount of fluid and cells from the suspicious area.
Core needle biopsy. A core biopsy uses a slightly larger, hollow needle with a special tip to obtain a cylinder of tissue. It is often done instead of a fine needle aspiration biopsy because it provides more tissue for the pathologist to analyze.
Vacuum-assisted biopsy. This type of biopsy uses vacuum pressure (suction) to collect the sample tissue through a specially designed hollow needle. This technique allows the doctor to collect multiple or larger samples from the same biopsy site without having to insert the needle more than once.
Image-guided biopsy. An image-guided biopsy is a procedure in which the doctor uses imaging technology, such as ultrasound, fluoroscopy, a computed tomography (CT or CAT) scan, x-ray, or a magnetic resonance imaging (MRI) test, to determine the exact location where the tissue sample will be removed for analysis. (Find more information about these imaging tests is in the next section of this article.) An image-guided biopsy may be used when a suspected tumor appears on an imaging scan, such as an x-ray, but cannot be felt or seen by the doctor. Once the area to biopsy is located, a needle is used to obtain a sample of the tissue from the site. The type of imaging technology used depends on the location of the biopsy site and other factors.
Surgical biopsy. In a surgical biopsy, a surgeon makes an incision in the skin and removes some or all of the suspicious tissue. It is often used if the needle biopsy shows evidence of cancer cells, or it may be used as the first method to obtain tissue for diagnosis. There are two types of surgical biopsies:
- An incisional biopsy is the removal of a piece of the suspicious area for examination. An incisional biopsy may be used for soft tissue tumors, such as those from muscle or fat, to distinguish between benign (noncancerous) lumps and cancerous tumors called sarcomas.
- An excisional biopsy removes the entire lump. An excisional biopsy was more commonly used before the development of fine needle aspiration, but it is still often used for enlarged lymph nodes or breast lumps, or in situations where the lump is small enough to be completely removed in one procedure.
Endoscopic biopsy. An endoscope is a tube with a camera that doctors use to view the inside of body, including the lung, bladder, abdomen, joints, or gastrointestinal (GI) tract. The person may be sedated as the tube is inserted into the body. An endoscope can be inserted through the mouth or a tiny surgical incision. Using an endoscope, the doctor can see any abnormal areas and remove tiny samples of the tissue using forceps that are part of the endoscope. For more information on the use of endoscopy, see below.
Bone marrow aspiration and biopsy. These two procedures are similar and often done at the same time. A bone marrow aspiration and biopsy is a diagnostic examination of the bone marrow, the red, spongy tissue inside of bone that has both fluid and solid parts. A bone marrow biopsy is the removal of a small amount of solid tissue using a hollow core needle. An aspiration removes a sample of fluid with a needle. A common site for a bone marrow biopsy and aspiration is the pelvic bone, which is located in the lower back by the hip. The skin in that area is usually numbed with medication beforehand, and other types of anesthesia (medication to block the awareness of pain) may be used. This test is used to determine if a person has a blood disorder or a blood cancer, such as anemia (a low level of red blood cells), leukemia, or multiple myeloma. It may also be used to find out if a cancer that started in another part of the body has spread to the bone marrow.
Doctors use imaging tests to determine whether the cancer has spread to other areas in the body and to evaluate the size and location of the tumor. Imaging tests alone are usually not specific enough to diagnose cancer.
X-ray. An x-ray is a way to create a picture of the structures inside of the body using a small amount of radiation. An x-ray is useful for finding and monitoring some types of tumors. Specific types of x-rays include mammography (an x-ray of the breast) and a barium enema (which is used in the x-ray of the colon and rectum).
Bone scan. 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.
CT or CAT scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail.
Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar or other substance is injected into a patient’s body and 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. Find out what to expect during a PET scan and an integrated PET-CT scan.
MRI. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium may be injected into a patient’s vein to create a clearer picture.
Ultrasound. An ultrasound uses sound waves to create a picture of the internal organs.
Any medical procedure performed with an endoscope is called an endoscopy. As explained above, an endoscope is a thin, flexible tube with a camera used to examine the inside of the body. The specific type of endoscope varies depending on what part of the body needs to be viewed. The following are some common examples of endoscopic tests:
- A bronchoscopy uses a bronchoscope to examine the lungs.
- A colonoscopy uses a colonoscope to examine the colon and rectum.
- A laparoscopy uses a laparoscope to examine the abdomen or pelvis.
Laboratory tests involve testing a sample of blood, urine, and/or other body fluids to learn or confirm what is happening in the body. One of the most common tests is a complete blood count (CBC). A CBC measures the components of the blood, including white blood cells, red blood cells, and platelets. Blood tests are also used to monitor potential side effects of cancer treatment, such as anemia or neutropenia (low white blood cell count), which can increase the risk of infection. Read about understanding blood test results.
Some tests help with diagnosing a specific type of cancer, such as the test for prostate specific antigen (PSA) for prostate cancer or the Pap test for the detection of cervical cancer. Other tests help doctors make treatment decisions. For example, the breast cells of women with breast cancer may be tested to determine whether the cells have the estrogen receptor, which lets doctors know whether hormone therapy can be used to treat the cancer.
Your doctor may also recommend running laboratory tests on a tumor sample to identify specific genes, proteins, and other factors unique to the tumor. Results of these tests will help decide whether your treatment options include a type of treatment called targeted therapy.
Finally, other tests using tumor markers help the doctors find out if cancer treatment is working. A tumor marker is a substance found in higher amounts in a person's blood, urine, or the tumor itself if the person has a specific type of cancer. It is produced by the tumor or the body in response to cancer, such as carcinoembryonic antigen (CEA) for colorectal cancer. However, these tests are only meaningful in specific situations. Learn more about ASCO's guidelines on tumor markers for gastrointestinal cancers, tumor markers for germ cell tumors, and tumor markers for breast cancer.