Do All Cancers Show Up on Blood Tests?

There are different types of cancers arising from various tissues all over the body. The method of diagnosis followed, the diagnostic tests or procedures used and the treatment plan would vary depending on the type of cancer. One or more of the following tests and procedures may be used to diagnose cancer:

Physical exam

Physical examination may be done to check for lumps, changes in skin color, enlarged organs, or other signs that could indicate the presence of cancer.

Laboratory tests

Laboratory tests help identify abnormalities that could be caused by cancer. High or low levels of certain substances in the body can be a sign of cancer. Some laboratory tests include

• Blood tests to evaluate organ functions (kidney, liver)
• Complete blood count (CBC)
• Urine test
• Tumor marker test
• Fecal occult blood test (test for traces of blood in the stools that is not visible to the naked eye)

Biopsy

During a biopsy, a sample of the tumor tissue is removed and examined under a microscope. Normal cells appear uniform and orderly whereas cancer cells will appear disorganized and irregular.

Biopsy samples can be collected in several ways. The type of biopsy procedure depends on the type of cancer and its location.

• Needle biopsy: A needle is used to withdraw sample tissue or fluid. This technique is used for spinal taps, bone marrow aspirations, and breast, prostate, and liver biopsies.
• Endoscopic biopsy: A thin, lighted tube called an endoscope is used to investigate areas inside the body. Sample cells or tissues are removed through the tube.
• Surgical biopsy: A part or all the tumor is removed by surgical procedure and sent for testing.
• Skin biopsy: A small sample of skin is removed in suspected skin cancer.
• Liquid biopsy: Liquid biopsy is a blood test that scans for traces of markers of certain cancers.

Imaging tests

Imaging tests create pictures of areas inside the body, which help to locate a tumor and areas where cancer has spread.

Some common types of imaging test include

• Computed tomography (CT) scan: A CT scan takes detailed 3-D images of organs from different angles using an X-ray machine linked to a computer. During the CT scan, the patient lies still on a table that slides into a donut-shaped scanner. The CT machine moves around the person taking pictures. Before the scan, a dye or other contrast material is administered using an intravenous (IV) catheter or via the oral or rectal opening to highlight certain areas in the body to make the pictures easier to read.
• Ultrasound: An ultrasound uses high-energy sound waves that echo off tissues inside the body. A computer uses these echoes to create pictures (sonograms) of areas inside the body.
• Magnetic resonance imaging (MRI): MRI uses a powerful magnet and radio waves to take pictures of the body in slices. These slices create detailed images of the inside of the body that show the difference between healthy and unhealthy tissues. During an MRI, the patient lies still on a table that is pushed into a long round chamber linked to a computer to capture images of the inside of the body.
• Nuclear scan: Nuclear scan, also called a radionuclide scan, uses radioactive material to take pictures of the inside of the body. Before the scan, a small amount of radioactive material called a tracer is injected that collects in certain organs or bones. A scanner detects and measures the radioactivity in the body, creating images of organs or bones on a computer screen or film.
• Positron emission tomography (PET) scan: PET scan is a type of nuclear scan that makes detailed 3-D pictures of areas inside the body where glucose is taken up. Before the scan, an injection of a tracer called radioactive glucose is administered. During the scan, the patient lies still on a table that moves back and forth through a scanner. Because cancer cells often take up more glucose, the pictures help find cancer in the body.
• Bone scan: Bone scans are a type of nuclear scan that is used to diagnose bone cancer or cancer that has spread to the bones. Before this test, a small amount of radioactive material is injected into the vein, which collects in abnormal areas in the bone. Hot spots or areas where the material collects can be seen in the pictures taken by a special scanner.
• X-ray: Low doses of radiation are used to create pictures of the inside of the body on an X-ray film.

Endoscopy procedures

An endoscope is used to view the inside of the body to find cancer. Endoscopes go through natural openings in the body, such as the mouth or anus. Common types of endoscope exams include

• Bronchoscopy
• Colonoscopy
• Cystoscopy
• Laparoscopy
• Laryngoscopy
• Mediastinoscopy
• Sigmoidoscopy
• Thoracoscopy
• Upper endoscopy

Other tests:

Several other tests may be suggested depending on the type of cancer that is suspected. Some common tests include

• Pap smear test for cervical cancer
• Mammography for breast cancer
• Myelogram for tumors in the spinal cord or nerve roots
• Gene testing