Cancer Diagnosis

Cancer Diagnosis

Reviewed By:
Mark Oren, M.D., FACP

Summary

A variety of tests are used to diagnose, classify and monitor the progress of cancer in individuals. These tests may be used to diagnose the disease after signs and symptoms have developed, or look for certain cancers before any indications arise.

Screening tests are tests used to detect certain types of cancer before symptoms develop. In their early stages, a number of cancers can be detected with screening tests, including:

  • Colorectal cancer
  • Prostate cancer
  • Breast cancer
  • Cervical cancer
  • Skin cancer
  • Some lung cancers

When patients show signs of cancer, physicians may order a variety of tests to detect the disease, determine the exact type of cancer and monitor the disease’s progression. Additional tests may also be used to determine if the disease has spread to other areas of the body (metastasized).

In order to diagnose cancer, a physician must almost always perform a biopsy. A biopsy is a procedure in which a small sample of tissue is collected and examined under a microscope. Additional tests used to diagnose and classify cancer include laboratory tests (e.g., blood tests, urine tests) and imaging tests (e.g., x-rays, CAT scan).

These tests are important because, in some cases, they allow for early detection of cancer. Finding cancer early is then beneficial because it may improve a patient’s prognosis (outlook). The tests also provide essential information needed by the patient’s cancer care team to make treatment decisions.

This guide focuses on diagnostic tests.

About cancer diagnosis

A variety of tests are used to diagnose cancer. They may be used to:

  • Detect the cancer

  • Establish the type of cancer

  • Determine characteristics of the cancer that may aid treatment decisions

  • Determine whether the cancer has spread to neighboring tissue or distant areas of the body (metastasis) and where it may have spread

While used for diagnosis, test results are also used by the patient’s cancer care team to choose the best treatment plan. Tests fall into two general categories:

  • Screening tests. These may be used routinely to detect certain types of cancer before signs and symptoms develop. Not all types of cancer have effective screening tests. The types that can be screened include:
    • Breast cancer
    • Cervical cancer
    • Colorectal cancer
    • Prostate cancer
    • Skin cancer
    • Some lung cancers

  • Staging tests. These are ordered after a patient shows signs or symptoms of disease to determine the nature and extent of the disease. Diagnostic testing usually involves:
    • Blood and tissue tests. Samples of blood or body tissue are taken for laboratory examinations.

    • Imaging tests. Tests that produce images of body structures.

The types of tests ordered vary depending on the type of cancer suspected or diagnosed.

There are many studies currently being conducted in the area of cancer diagnosis. Researchers are trying to improve current tests and develop new testing techniques to better detect the disease. Diagnostic tests are considered an important research subject because, in some cases, they allow for early detection of the disease. Finding cancer early is beneficial because it often improves a patient’s prognosis (outlook).  

Screening tests for cancer

In its early stages, cancer may not produce any symptoms. However, there are screening tests that make it possible to detect certain types of cancer before symptoms occur.

Two of the most important tools in early detection of cancer are medical history and physical examination. When providing their medical history, patients will give information about their past and present medical conditions and medications, as well as the medical information of their family members. A physical examination is the process by which a physician carefully inspects various organ systems and other parts of the patient’s body for signs of illness.

Common screening tests for cancer include:

  • Pap smear. Collection of a sample of cells from the cervix and upper vagina. The cells are then examined for abnormalities under a microscope. This test may be used to detect cervical cancer. The American Cancer Society (ACS) recommends that all women begin having annual Pap smears about three years after they begin to have vaginal intercourse, but no later than 21 years of age. Newer liquid-based Pap smears may be conducted every two years. The screening interval may vary to every three years for women over 30 who have had three consecutive normal Pap smears.

  • Mammogram. X-ray image of the breast that is examined for the presence of an abnormal tissue mass or infiltrates. The test may be used to detect breast cancer. According to the ACS, women at an average risk for breast cancer should have yearly mammograms starting at age 40. Women in their 20s and 30s should have clinic breast exams as part of their regular health examinations, every three years. Monthly breast self exams should also be part of a woman’s regular routines beginning in their early 20s. Some physicians may recommend breast MRIs for women at higher risk for breast cancer.

  • Prostate specific antigen (PSA). A blood test that measures the amount of PSA (a protein produced by the prostate) in the blood. It may be used to detect prostate cancer. The ACS recommends that men at an average risk for prostate cancer have an annual PSA test beginning at the age of 50. Men at higher risk for prostate cancer (e.g., black men or those with a family history of prostate cancer) should begin at age 45.

  • Digital rectal examination (DRE). Insertion of a gloved finger into the rectum to feel for anything abnormal. This exam may be used to detect rectal or prostate cancer. The ACS recommends that men at an average risk for prostate cancer have an annual DRE beginning at the age of 50. As with the PSA test, men at higher risk for prostate cancer should begin at age 45.

  • Fecal occult blood test (FOBT). Laboratory examination of a sample of feces for the presence of blood. It may be used to detect colorectal cancer. According to the ACS, a person at an average risk of developing colorectal cancer can benefit from having a yearly FOBT beginning at the age of 50.

  • Sigmoidoscopy. A flexible lighted instrument (sigmoidoscope) is placed in the rectum and lower colon to detect precancerous and cancerous growths. It may be used to detect colorectal cancer. According to the ACS, a person at an average risk of developing colorectal cancer can benefit from having a sigmoidoscopy every five years beginning at the age of 50. However, the more thorough colonoscopy may be ordered in some cases.

  • Colonoscopy. A lighted instrument (colonoscope) is used to examine the colon for precancerous or cancerous growths. It may be used to detect colorectal cancer. According to the ACS, a person at an average risk of developing colorectal cancer can benefit from having a colonoscopy every 10 years beginning at the age of 50.

  • Skin inspection. An inspection by a dermatologist for any abnormalities of the skin. This screening is particularly important in fair-skinned, blue eyed individuals who are exposed to the sun. It is also important for people with moles or skin abnormalities that have changed. A yearly inspection is a desirable schedule.

Each patient should discuss their individual screening schedule with their physician. People at an increased risk of developing cancer may be required to start screening earlier, have additional tests, or have more frequent exams.

Blood and tissue tests for cancer

A variety of tests may be ordered to diagnose, classify, and monitor cancer.  Samples of cells from the patient’s blood and bone marrow will be examined to verify the diagnosis. Tests will also be used to determine if the cancer has spread to the lymphatic system, central nervous system (brain and spinal cord) or to other areas of the body. Additional tissue and cell samples may also be needed to guide treatment.

In order to diagnose cancer, a physician nearly always performs a biopsy. This procedure involves removing a small sample of tissue and examining it under a microscope. There are many different types of biopsies. Some biopsies involve surgery to remove an entire organ, while others are much less invasive. The biopsies most often used in diagnosing cancer include:

  • Needle biopsy. A needle is inserted into the tumor and fluid and cells are aspirated (drawn out) with a vacuum syringe. There are two major types of needle biopsy:
    • Fine needle aspiration (FNA). A thin needle and a syringe are used to remove a small amount of fluid and tissue.

    • Core biopsy. A slightly larger needle is used to remove a cylinder of tumor tissue that is typically 1/16 inches (0.16 centimeters [cm]) in diameter and 1/2 inch (1.27 cm) long. 

  • Surgical biopsy. There are two types of surgical biopsy:
    • Excisional biopsy. Used with smaller tumors. A surgeon makes an incision in the skin and removes the entire tumor.

    • Incisional biopsy. Used with larger tumors. A surgeon makes an incision in the skin and removes a small part of the tumor.

  • Endoscopic biopsy. A thin, flexible tube with a fiberoptic light and a viewing lens or video camera is inserted into the patient through a natural body opening, such as the rectum, mouth or throat. This allows the physician to see a tumor up close and to insert an instrument through the tube to remove a sample for analysis. This type of biopsy may be used to diagnose colorectal and lung cancers, among others.

  • Laparoscopy and thoracoscopy. Laparoscopy is similar to an endoscopy. A small incision is made in the abdomen to examine the contents and remove tissue samples. A thoracoscopy is the same procedure, except it is used to view the inside of the chest.

  • Laparotomy and thoracotomy. Laparotomy is a surgical technique that uses an incision in the upper abdomen to explore a suspicious area. It is done when less invasive techniques are inconclusive. This method can reveal information about the location and size of the tumor, and the involvement of surrounding areas. The procedure is known as a thoracotomy when the chest area is explored.

  • Paracentesis or thoracentesis. A needle is used with local anesthesia to remove fluid samples from the abdomen or chest. Paracentesis refers to the removal of abdominal fluid whereas thoracentesis is the medical term for the removal of fluid in the chest.

  • Bone marrow aspiration and biopsy. A bone marrow aspiration involves using a thin needle to collect a small sample of liquid bone marrow. A bone marrow biopsy uses a larger needle to remove a piece of bone marrow. These procedures are usually performed at the same time, under local anesthesia.

  • Sentinel lymph node biopsy. Biopsy of the first node that receives lymphatic drainage from a tumor. This is done to check how far a cancer has spread. If cancerous cells are found in this lymph node, other nearby lymph nodes may be removed in a procedure known as a lymph node dissection.

Other tests used in the diagnoses and classification of cancer include:

  • Spinal tap. Also known as a lumbar puncture, this procedure uses a needle to remove a sample of cerebrospinal fluid (CSF) from between the bones in the lower spine. The sample is then examined for cancer cells.

  • Additional blood tests. A blood test uses a sample of blood to detect and measure various factors in the blood.

  • Urine tests. A urine test uses a sample of urine to diagnose diseases of the urinary system and other body systems.

A variety of laboratory processes are used to examine samples once they are taken, allowing the pathologist to diagnose and classify the cancer. These include:

  • Routine microscopic exam. All samples (e.g., bone marrow, lymph node tissue, blood, CSF) are studied under a microscope by a pathologist. A number of characteristics, including the size and shape of the cells, are noted in order to classify the cancer cells into specific types.

  • Complete blood count. A complete blood count (CBC) is a blood test that measures the number of red blood cells, white blood cells and platelets in a sample of blood, as well as the amount of hemoglobin in the red blood cells and a number of other factors. Changes in the numbers of different blood cell types and the appearance of the cells can suggest cancer.

  • Blood chemistry tests. These tests measure the level of specific chemicals in the blood. They are used to monitor changes in liver or kidney function caused by cancer or treatment with certain chemotherapy drugs. The tests may also be ordered to determine whether treatment is required to correct abnormally low or high levels of certain minerals.

  • Cytochemistry. This test involves placing cells on glass microscope slides and exposing them to chemical stains. The stains then react with certain types of cancer cells and change color. The color changes, or lack there of, are then detected under a microscope. The test may be ordered to distinguish one form of cancer from another.

  • Flow cytometry. Fluorescent antibodies are used to detect certain molecules on the surface of cancer cells. The cells being examined are treated with the antibodies, each of which attaches itself to a certain type of molecule. The cells are passed in front of a laser beam which causes the cells to give off light of a different color. The color is then measured and analyzed by a computer. This test may be ordered to determine the exact type of cancer or to distinguish cancer from other diseases. 

  • Cytogenetics.  The genetic characteristics of cells are evaluated under a microscope. It may be ordered to determine if the cells have too many chromosomes, or if the chromosomes have any:
    • Translocations. The transfer of DNA from one chromosome to another. Identifying translocations helps to distinguish certain types of cancer and is important in determining the patient’s prognosis (outlook).

    • Inversions. The rearrangement of DNA in part of a chromosome.

    • Deletions. The loss of part of a chromosome.

    • Additions. A chromosome (all or part) is duplicated and too many copies are found in a cell.

      In addition to diagnosing and classifying cancer, cytogenics is also useful in determining a person’s risk of developing the disease. Genetic tests are currently available to identify some oncogenes and some genetic abnormalities predisposing to cancer. For example, the BRCA1 and BRCA2 genes predispose some women to developing breast cancer. Women who know they have some family history of breast cancer should speak to their physicians about the suitability of genetic testing.  
  • Immunocytochemistry (immunophenotyping). This procedure uses special antibodies to detect certain molecules on the surface of cancer cells. The cells being examined are treated with the antibodies, each of which attaches itself to a certain type of molecule. The cells containing these molecules then change color. The cells are then examined under a microscope. This test may be ordered to determine the exact type of cancer or to distinguish cancer from other diseases. 

  • Molecular genetic studies. These tests examine cancer cell DNA. They may be ordered to detect translocations that are too small to detect under a microscope with cytogenic tests. Molecular genetic studies are useful in classifying cancer because many of its subtypes have distinctive translocations. Information about the translocations can also be used to predict the patient’s response to treatment. After treatment, the tests may be ordered to detect cancer cells that can be missed under a microscope.

Imaging tests for cancer

Imaging tests are capable of producing images of the inside of the body. Although imaging tests cannot be used to determine if a tumor is malignant (cancerous), they can be used to locate a tumor, measure its size and determine if growth has occurred since previous testing. Imaging tests used in diagnosing cancer include:

  • Computed axial tomography (CAT) scan (also known as a computed tomography or CT scan). Allows for multiple x-rays to be taken from different angles around the patient. The “slices” or cross–sectional images of the patient’s body are analyzed by a computer.  CAT scans give a physician an enhanced look at the lymph nodes in the head, neck, chest, abdomen, pelvis and in some organs. CAT scans may also be used to guide a biopsy needle into an enlarged lymph node or organ located deep in the body. This procedure is known as a CAT-guided needle biopsy.
  • Magnetic resonance imaging (MRI). Uses a powerful magnetic field to create images of structures and organs within the body, allowing a computer to produce very clear cross-sectional or three-dimensional images. It may be ordered to determine if the disease has spread to a variety of organs, for example, the spinal cord or brain.

  • Positron emission tomography (PET) scan. Involves the injection of glucose (sugar) containing a small amount of radioactive material. Once in the body, the radioactive glucose is absorbed by the cancer cells. A camera then scans the patient and detects where the radioactive glucose was absorbed.

  • X-rays. An image is created of part of the body by using low doses of electromagnetic radiation that are reflected on film paper or fluorescent screens.

  • Ultrasound. High-frequency sound waves are used to produce images of internal organs. This test is useful for detecting enlarged kidneys, liver or spleen.

  • Single-photon emission computed tomography (SPECT). Involves radioactive tracers containing antibodies that attach to tumors, making them more visible. Like a CT scan, it uses a rotating camera that creates cross-sectional image “slices” of the body.

  • Bone scan. A radioactive substance is injected into the bloodstream where it travels to areas of damaged bone, making it more detectable to a camera that slowly scans the body. The test is helpful in locating bone damage due to cancer in the bones.

Sometimes imaging tests may be used in combination. For example, CAT scans combined with PET scans have proved useful for both detecting some head and neck cancers and analyzing the cancer’s stage. Some specific new technologies are being developed to combine the scans, which may also be valuable for other cancers and in obese patients. New types of contrast agents to use with PET scans are also being developed.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians about their condition. Patients may wish to ask their doctors the following questions about cancer diagnosis:

  1. What kind of tests can be used to screen for cancer?
  2. If screening tests are positive, what is the next step?
  3. Are there regular screening tests I should be getting?
  4. What can blood tests tell about my diagnosis?
  5. What kind of biopsy will I have?
  6. When and from whom will I receive my biopsy results?
  7. If I have already been treated for cancer, are there additional tests I should have to monitor for new cancers or recurrences?
  8. Can one test provide more information than another about my cancer?
  9. Will any of these tests be used to help decide a treatment regimen?
  10. Are there any risks associated with these tests?
  11. How often should I have the screening or diagnostic tests you recommend?
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