If your doctor suspects that you have cancer, you'll likely first talk about your medical history and have a physical exam. If these indicate the possibility of cancer, you'll then need one or more tests to help determine whether it is cancer. If it's cancer, findings from these tests — which may include blood and urine analyses, diagnostic imaging techniques and biopsy — help your doctor determine where the cancer is and how far it has spread (staging). This information is key in planning what specific treatment you'll need.

Understanding what to expect during the process of cancer diagnosis — from a physical exam to biopsy — and how your doctor arrives at a diagnosis may help enable you to ask more-informed questions and feel more comfortable with your diagnosis and treatment.

If you're experiencing signs or symptoms that may indicate cancer, your doctor typically starts by asking you for information about your medical history and by giving you a physical exam. Medical information that the doctor may ask about includes detailed accounts of:

• Your current health, including any current physical complaints
• Your past health, including prior medical conditions
• Your family's history of illness, including cancer
• Any environmental exposures that might put you at risk of cancer

A thorough physical exam then allows your doctor to further evaluate your overall health. The doctor examines your entire body, listening to your heart and lungs and checking for any lumps or bumps, with particular focus on areas of concern. For men, the exam includes examination of the testicles, prostate and rectum. For women, it includes examination of the breasts, pelvis and rectum.

If your medical history and physical exam suggest the need for further testing, your doctor may use blood and urine tests to help rule out or diagnose disease. Small amounts of blood and urine are collected and then, in a laboratory, are analyzed for abnormalities.

Blood is typically obtained from one of your veins — such as a vein inside your forearm — by using a thin needle inserted through your skin. In some instances, blood may be obtained by pricking your fingertip. For a urine test, you collect a urine sample in a small container.

Afterward, your blood and urine are tested in a lab. If cancer cells, abnormal numbers or types of blood cells, or any of various other substances are detected, they may indicate cancer. For example, if you have leukemia — a blood cancer — cancerous white blood cells can be seen under a microscope.

Higher-than-normal levels of certain antigens, proteins and other substances (tumor markers) in your blood or urine also might suggest the presence of cancer. However, tumor marker test results need to be interpreted carefully, as noncancerous conditions also can cause abnormal results.

Though blood and urine tests can help diagnose your disease, other tests are usually necessary to make the diagnosis.

Diagnostic imaging tools, such as X-ray and magnetic resonance imaging (MRI), allow your doctor to create pictures of your bones, organs and other areas inside your body. These images can help your doctor determine whether you have a tumor, where in your body it's located, how large it is and if it has spread. Your doctor determines which areas of your body to examine and which tests to use based on your particular situation. Commonly used imaging techniques include:

• X-ray. X-rays are a form of radiation that can make images (radiographs) of your bones and internal organs. In an X-ray exam, carefully aimed X-rays produce an image on X-ray film or a digital recording device.

  Tissues differ in their tendency to absorb or transmit X-rays. Bone absorbs much of the X-rays, which prevents them from reaching the film, and creates a white image. Air, however, transmits X-rays, allowing them to pass through to the film and create a darker image. For example, normal, air-filled lung tissue appears dark on film. One use of X-ray in diagnosing cancer is to see if cancer has spread to the lungs. If it has, the cancer may appear as lighter in color on the film than does the surrounding, normal lung tissue. X-rays also might be used to examine cancers of the intestines, stomach, liver, spleen, kidneys and breasts.

• Computerized tomography (CT). Computerized tomography is an X-ray technique that produces more-detailed images of your internal organs than do conventional X-ray studies. This procedure uses an X-ray tube — that rotates around your body — and a large computer to create cross-sectional images (like slices) of the inside of your body. When images are combined, the doctor can clearly see tumors, accurately measure them and later biopsy them if necessary. CT can pinpoint a tumor or infection deep in the brain, abdomen or chest and is the best way to evaluate your lungs for evidence of tumor spread. CT scans are typically used to examine your brain, lungs, liver, pancreas, adrenal glands and bones.

• Magnetic resonance imaging (MRI). Like computerized tomography, MRI also views the inside of your body in cross-sectional slices, but it uses an extremely strong magnet instead of X-rays. The magnet manipulates water molecules in your body so that they tumble, which produces a very faint signal. A very sensitive receiver — like a radio antenna — then picks up those signals. A computer used to generate the pictures manipulates the resulting signal. Depending on their chemical makeup, different tissues, such as tumors, produce a stronger or weaker signal. In some cases MRI can be a more sensitive test than CT. MRI is often used to detect cancer of the brain, spinal cord, head and neck.

• Ultrasonography. Ultrasound technology works by bouncing high-frequency sound waves off tissues in your body, to form images on a small monitor (television screen). Special crystals inside a small plastic device known as a transducer direct these waves (pulses) of sound into the area that's being imaged. Sound waves reflect off tissues and are collected by the same transducer. This information is sent to a computer that composes images based on patterns created by the sound waves.

  Ultrasound can be used to look for tumors and to help guide needle biopsies. During a biopsy, a piece of tissue is removed for examination using a microscope to help establish a diagnosis. By using ultrasound during these procedures, doctors can better determine the exact area from which to take the tissue sample. Ultrasound is also typically helpful in diagnosing cancers found in soft tissues. For example, it can be used to help determine whether a mass found in your breast is a fluid-filled cyst or a solid tumor.

• Radionuclide scanning. In a radionuclide scan, your doctor injects a small, safe amount of radioactive material into your bloodstream. All of your tissues and bones absorb some of this material. Tumors may absorb more or less of it, however, and appear differently from surrounding, healthy tissue. A camera then passes over your body to scan for these areas. Radionuclide scans can help the doctor locate tumors, particularly of your bones or thyroid.

• Positron emission tomography (PET). During a PET scan, your doctor injects a small amount of a radioactive tracer — typically a form of glucose — into your body. All tissues in your body absorb some of this tracer, but tissues that are using more energy — exhibiting increased metabolic activity — absorb greater amounts. Tumors are often more metabolically active than healthy tissues are and may absorb more of the tracer, which allows the tumors to appear on the scan.

  PET scans can help doctors determine the location of a tumor and see if it has spread. For example, in the past, doctors could only determine whether cancer had spread to the lymph nodes if there was evidence of lymph node enlargement. PET scanning now enables doctors to detect cancer in a lymph node before enlargement occurs, allowing for earlier detection and treatment of the cancer. However, PET test results need to be interpreted carefully, as noncancerous conditions can resemble cancer.

A biopsy — the removal of a sample of tissue for study, generally under a microscope — is always necessary to make a cancer diagnosis. Sample tissue may be removed by using techniques that commonly include:

• Needle biopsy. Your doctor uses a thin needle and a syringe to remove small pieces of tissue from a tumor. Two types of needle biopsy exist — fine-needle aspiration and core biopsy. These procedures are essentially the same, but a core biopsy involves using a slightly larger needle to remove a small, solid core of tissue.
• Endoscopic biopsy. Your doctor inserts a thin, flexible tube (endoscope) into a natural opening in your body, such as your rectum or lung. The endoscope contains a fiber-optic light and a video camera at its tip. The camera lens transmits images to an external monitor so that your doctor can look closely at areas inside your body. If the doctor sees abnormal looking tissue, he or she can insert instruments through the endoscope to remove sample tissue.
• Surgical biopsy. Your doctor makes an incision through your skin and removes either an entire tumor (excisional biopsy) or a portion of a tumor (incisional biopsy). In some cases you may only need local anesthesia. Other times, such as when a tumor is inside your chest, your doctor may use general anesthesia.

After the doctor obtains a tissue sample, it's generally chemically treated and sliced into very thin sections. These sections are placed on glass slides, stained — to enhance contrast — and studied under a microscope by a pathologist (a person who specializes in examining body tissues), a hematologist (a specialist in blood and blood-forming tissues) or both. This allows the pathologist to determine exactly where the cancer came from and the grade of the cancer. The grade — an assigned number on a scale of 1 to 4 — refers to the appearance of cancer cells under the microscope. Grade 1 cancers are generally the least aggressive and grade 4 cancers, the most aggressive. This information may help guide treatment options.

With the information gathered during tests such as imaging and biopsy, your doctor then determines the stage of your cancer. Staging is a system of classifying information about cancer, including the size of your tumor, how much it has spread in your body and to where it has spread. Roman numerals between 0 and IV are used to describe stages, 0 being the least advanced, IV being the most advanced. Your doctor uses this information to determine what treatment you need and to evaluate how your cancer might progress. For example, if advanced stage cancer has been determined, it may require more aggressive treatment than that of an early-stage cancer.