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Diagnosis of Cancer


Robert Peter Gale

, MD, PhD, DSC(hc), Imperial College London

Reviewed/Revised Oct 2022
Topic Resources

Cancer is suspected based on a person's symptoms, the results of a physical examination, and sometimes the results of screening tests Imaging tests Cancer is suspected based on a person's symptoms, the results of a physical examination, and sometimes the results of screening tests. Occasionally, x-rays obtained for other reasons, such as... read more . Occasionally, x-rays obtained for other reasons, such as an injury, show abnormalities that might be cancer. Confirmation that cancer is present requires other tests (termed diagnostic tests).

After cancer is diagnosed, it is staged. Staging Staging Cancer Cancer is suspected based on a person's symptoms, the results of a physical examination, and sometimes the results of screening tests. Occasionally, x-rays obtained for other reasons, such as... read more is a way of describing how advanced the cancer has become, including such criteria as how big it is and whether it has spread to neighboring tissues or more distantly to lymph nodes or other organs.

Imaging tests


Cancer is confirmed by obtaining a piece of the tumor through needle biopsy or surgery and finding cancer cells on microscopic examination of samples from the suspected area. Usually, the sample must be a piece of tissue, although sometimes examination of the blood is adequate (such as in leukemia). Obtaining a tissue sample is termed a biopsy.

Biopsies can be done by cutting out a small piece of tissue with a scalpel, but very commonly the sample is obtained using a hollow needle. Such tests are commonly done without the need for an overnight hospital stay (outpatient procedure). Doctors often use ultrasonography or CT to guide the needle to the right location. Because biopsies can be painful, the person is usually given a local anesthetic to numb the area.


Tumor markers

When examination findings or imaging test results suggest cancer, measuring blood levels of tumor markers (substances secreted into the bloodstream by certain tumors) may provide additional evidence for or against the diagnosis of cancer. In people who have been diagnosed with certain types of cancer, tumor markers may be useful to monitor the effectiveness of treatment and to detect possible recurrence of the cancer. For some cancers, the level of a tumor marker drops after treatment and increases if the cancer recurs.

Some tumor markers cannot be measured in the blood but instead can be found on tumor cells. These markers are found by examining tissue from a biopsy sample. HER2 and EGFR are examples of tumor markers found on tumor cells.


Staging Cancer

After cancer is diagnosed, staging tests help determine how extensive the cancer is in terms of its location, size, growth into nearby structures, and spread to other parts of the body. People with cancer sometimes become impatient and anxious during staging tests, wishing for a prompt start of treatment. However, staging allows doctors to determine the most appropriate treatment as well as help to determine prognosis.

Staging may use scans or other imaging tests, such as x-rays X-Rays X-rays are a type of medical imaging that use very low-dose radiation waves to take pictures of bones and soft tissues. X-rays may be used alone (conventional x-ray imaging) or combined with... read more , CT Computed Tomography (CT) Computed tomography (CT) is a type of medical imaging that combines a series of x-rays to create cross-sectional, detailed images of internal structures. In computed tomography (CT), which used... read more Computed Tomography (CT) , MRI Magnetic Resonance Imaging (MRI) Magnetic resonance imaging (MRI) is a type of medical imaging that uses a strong magnetic field and very high frequency radio waves to produce highly detailed images. During an MRI, a computer... read more Magnetic Resonance Imaging (MRI) , bone scans with radioactive materials Radionuclide Scanning Radionuclide scanning is a type of medical imaging that produces images by detecting radiation after a radioactive material is administered. During a radionuclide scan, a small amount of a radionuclide... read more , or positron emission tomography Positron Emission Tomography (PET) Positron emission tomography (PET) is a type of medical imaging called radionuclide scanning. By detecting radiation after a radioactive material is administered, PET creates images that can... read more Positron Emission Tomography (PET) (PET). The choice of staging test(s) depends on the type of cancer. CT is used to detect cancer in many parts of the body, including the brain and lungs and parts of the abdomen, including the adrenal glands, lymph nodes, liver, and spleen. MRI is of particular value in detecting cancers of the brain, bones, and spinal cord.

Biopsies are often needed to confirm the presence of tumor for staging purposes and can sometimes be done together with the initial surgical treatment of a cancer Surgery for Cancer Surgery is a traditional form of cancer treatment. It is the most effective in eliminating most types of cancer before it has spread to lymph nodes or distant sites (metastasized). Surgery may... read more . For example, during a laparotomy (an abdominal operation) to remove colon cancer, a surgeon removes nearby lymph nodes to check for spread of the cancer. During surgery for breast cancer, the surgeon biopsies or removes a lymph node located in the armpit (the first lymph nodes to which cancer is likely to spread, also called a sentinel lymph node) to determine whether the breast cancer has spread there. Evidence of spread, along with features of the primary tumor, helps the doctor determine whether further treatment is needed.

When staging is based only on initial biopsy results, physical examination, and imaging, the stage is referred to as clinical. When the doctor uses results of a surgical procedure or additional biopsies, the stage is referred to as pathologic or surgical. The clinical and pathologic (surgical) stages may differ.

In addition to imaging tests, doctors often obtain blood tests to see if the cancer has begun to affect the liver, bones, or kidneys.

Grading Cancer

Grading is a measure of how quickly the cancer is growing or spreading (called aggressiveness). A cancer's grade can help doctors determine prognosis. Grade is determined by examining the tissue specimen obtained during a biopsy. Grade is based on the degree of abnormality of the appearance of cancer cells on microscopic examination. More abnormal appearing cells are more aggressive. For many cancers, grading scales have been developed.

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