Cancer is nearly always diagnosed by an expert who has looked at cell or tissue samples under a microscope. In some cases, tests done on the cells’ proteins, DNA, and RNA can help tell doctors if there’s cancer. These test results are very important when choosing the best treatment options.Tests of cells and tissues can find many other kinds of diseases, too. For instance, if doctors are not sure a lump is cancer, they may take out a small piece of it and have it tested for cancer and for infections or other problems that can cause growths that may look like cancer.
Your doctor may use one or more approaches to diagnose cancer:
Your doctor may feel areas of your body for lumps that may indicate a tumor. During a physical exam, he or she may look for abnormalities, such as changes in skin color or enlargement of an organ, that may indicate the presence of cancer.
Laboratory tests, such as urine and blood tests, may help your doctor identify abnormalities that can be caused by cancer. For instance, in people with leukemia, a common blood test called complete blood count may reveal an unusual number or type of white blood cells.
Imaging tests allow your doctor to examine your bones and internal organs in a noninvasive way. Imaging tests used in diagnosing cancer may include a computerized tomography (CT) scan, bone scan, magnetic resonance imaging (MRI), positron emission tomography (PET) scan, ultrasound and X-ray, among others.
During a biopsy, your doctor collects a sample of cells for testing in the laboratory. There are several ways of collecting a sample. Which biopsy procedure is right for you depends on your type of cancer and its location. In most cases, a biopsy is the only way to definitively diagnose cancer.
When a lump, or a bump is discovered in superficial areas of the body such as the breast and neck, a test known as Fine Needle Aspiration Cytology (FNAC) is recommended to determine whether the lump is cancer. This procedure is also used to test for thyroid, salivary glands and lymph nodes illnesses.
In the laboratory, doctors look at cell samples under the microscope. Normal cells look uniform, with similar sizes and orderly organization. Cancer cells look less orderly, with varying sizes and without apparent organization.
A computed tomography (CT or CAT) scan allows doctors to see inside your body. It uses a combination of X-rays and a computer to create pictures of your organs, bones, and other tissues. It shows more detail than a regular X-ray.
You can get a CT scan on any part of your body. The procedure doesn't take very long, and it's painless.
How Do CT Scans Work?
They use a narrow X-ray beam that circles around one part of your body. This provides a series of images from many different angles. A computer uses this information to create a cross-sectional picture. Like one piece in a loaf of bread, this two-dimensional (2D) scan shows a "slice" of the inside of your body.
An MRI scan uses a large magnet, radio waves, and a computer to create a detailed, cross-sectional image of internal organs and structures.
The scanner itself typically resembles a large tube with a table in the middle, allowing the patient to slide in.
An MRI scan differs from CT scans and X-rays, as it does not use potentially harmful ionizing radiation.
A positron emission tomography (PET) scan is an imaging test that allows your doctor to check for diseases in your body.
The scan uses a special dye containing radioactive tracers. These tracers are either swallowed, inhaled, or injected into a vein in your arm depending on what part of the body is being examined. Certain organs and tissues then absorb the tracer.
When detected by a PET scanner, the tracers help your doctor to see how well your organs and tissues are working.
The tracer will collect in areas of higher chemical activity, which is helpful because certain tissues of the body, and certain diseases, have a higher level of chemical activity. These areas of disease will show up as bright spots on the PET scan.
The PET scan can measure blood flow, oxygen use, how your body uses sugar, and much more.
A PET scan is typically an outpatient procedure. This means you can go about your day after the test is finished.
An X-ray, a type of high-energy electromagnetic radiation, is often used for medical imaging. X-ray technology may be used to examine many parts of the body. This image-guided technology is an important procedure for cancer diagnosis, staging and treatment.
An X-ray uses electromagnetic radiation to create images. The image is recorded on a film, called a radiograph. The images produced appear light or dark, depending on the absorption rates of the various tissues. For example, dense materials, such as bone, show up white on a film, while fat and muscle may appear in varying shades of gray.
Originally, X-rays were used for imaging bones because they were easily distinguishable from soft tissues on films available at the time. Today, improvements such as better photographic films, more accurate focusing systems and more sensitive detection methods have led to better imaging technology and results. Using lower-exposure levels, fine detail and subtle differences may be distinguished in tissue density. Advances in technology have led to the development of computed tomography (CT), which combines multiple X-ray images into a 3D model.
A valuable medical tool, the X-ray is a noninvasive procedure used for diagnosing disease, monitoring therapy and planning surgical treatment. X-rays may also be used in guiding the placement of medical devices such as catheters and stents.
Before undergoing certain types of X-rays, you may be given a contrast medium like barium or iodine to help identify a specific area of the body on the X-ray image. Contrast mediums may be swallowed or given as an injection or an enema.
An X-ray exam is quick and painless. In low doses, X-rays may be used to create images of structures inside the body to detect and stage a tumor. Radiation exposure from an X-ray for imaging is low, and research suggests the benefits far outweigh the risks. In higher doses, X-rays may be used in radiation therapy to help destroy cancerous cells in the body.