Doctors use many tests to diagnose cancer and find out if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy (the removal of a small amount of tissue for examination under a microscope) is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
• Type of cancer suspected
• Severity of symptoms
• Previous test results

In addition to a physical examination and biopsy, the following tests may be used to diagnose multiple myeloma:

Blood and urine tests. Myeloma cells secrete an antibody known as the M protein (monoclonal immunoglobulin). Levels of the M protein in a patient's blood and urine are used to determine the extent of the disease and to monitor the effectiveness of treatment. The levels of serum albumin (a blood protein made by the liver that is necessary for maintaining proper blood volume) and serum beta 2-microglobulin (β2-M, a small protein that plays a role in immunologic defense) are measured using blood tests; these results are important for staging [2]. Blood tests are also used to measure kidney function, calcium levels, and blood counts [3] (for possible anemia).

X-ray. An x-ray is a way to create a picture of the structures inside of your body using a small amount of radiation. X-rays are typically the first step in evaluating bones when myeloma is suspected or diagnosed.

Bone marrow biopsy and aspiration [4]. These two procedures are similar and often done at the same time. Bone marrow has both a solid and a liquid part. A bone marrow biopsy is the removal of a small amount of solid tissue using a needle, and it is important to making a diagnosis of myeloma. An aspiration removes a sample of fluid with a needle. The sample(s) are then analyzed by a pathologist, a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. A common site for a bone marrow biopsy and aspiration is the pelvic bone, which is located in the lower back by the hip. The skin in that area is usually numbed with medication beforehand, and other types of anesthesia (medication to block the awareness of pain) may be used. 

Fat pad aspirate. If M proteins are deposited in body tissues, it can cause organ dysfunction. This condition is called amyloidosis [5]. If amyloidosis is a consideration, it may be necessary to take a sample of the abdominal fat pad (the collection of fat around a person's abdomen) for examination under a microscope, called a biopsy.

Molecular testing of the tumor. Your doctor may recommend running laboratory tests on a tumor sample to identify specific genes, proteins, and other factors unique to the tumor. Results of these tests may help guide your treatment options (see Treatment [6]).

Magnetic resonance imaging (MRI) [7]. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. An MRI can show replacement of normal bone marrow by myeloma cells or plasmacytoma (a plasma cell tumor growing in bone or soft tissue), especially in the skull, spine, and pelvis. The detailed images may also show compression fractures of the spine or a tumor pressing on nerve roots. A contrast medium (a special dye) may be injected into a patient’s vein to create a clearer picture.

Computed tomography (CT or CAT) scan [8]. A CT scan creates a detailed, cross-sectional view that shows any abnormalities or tumors in soft tissues. A computer then combines these images into a three-dimensional picture of the inside of the body. Sometimes, a contrast medium is injected into a patient’s vein to provide better detail, but it is used cautiously in patients with multiple myeloma because of a risk of kidney failure.

Positron emission tomography (PET) scan [9]. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body. This substance is absorbed mainly by organs and tissues that produce the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.

Integrated PET-CT scan. [10] An integrated PET-CT scan combines the images from a positron emission tomography (PET) scan and a computed tomography (CT) scan, performed at the same time on the same machine. Together, the two scans create a more complete image than either test can offer alone.

Learn more about what to expect when having common tests, procedures, and scans [11].

After these diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer; this is called staging [2]. Learn more about the first steps to take after a diagnosis of cancer [12].