Bone Marrow Cancer (Myeloma) in Cats

By PetMD Editorial on May 22, 2010

Multiple Myeloma in Cats

Multiple myeloma is an uncommon cancer that is derived from a clonal population of cancerous (malignant) plasma cells in the bone marrow. A “clonal population of cells” is a group of cells that have descended from a single cell; all of them have the same genetic make-up. Plasma cells are specialized white-blood cells, lymphocytes that have been altered to produce immunoglobulin, an immune protein or antibody necessary for fighting disease.

Three of four defining features must be present for a diagnosis of multiple myeloma: immune protein from a single clone of cells (known as a monoclonal gammopathy), seen as a spike in the gamma region of a protein analysis of the blood (known as a protein electrophoresis); cancerous plasma cells or a high number of plasma cells in the bone marrow (known as plasmacytosis); destruction of areas of bone (known as lytic bone lesions); and a particular type of protein found in the urine (known as Bence Jones [light-chain] proteinuria).

Multiple myeloma occurs primarily in middle-aged or older cats (6-13 years).

Symptoms and Types


Attributed to bone infiltration and destruction of bone, effects of proteins produced by the tumor (such as increased protein in the blood leading to sludging of the blood and kidney damage), and infiltration of organ(s) by cancerous cells. Symptoms depend on location and extent of disease.

  • Weakness
  • Lameness
  • Generalized discomfort or uneasiness
  • Pain
  • Fever
  • Partial paralysis
  • Increased thirst
  • Increased urination
  • Urinary incontinence
  • Dementia
  • Labored breathing
  • Lack of appetite
  • Weight loss
  • Bleeding from the nose that may involve one or both nostrils
  • Bleeding in the back part of the eye and blindness
  • Excessive bleeding from needle punctures to collect blood or to administer intravenous medications and/or fluids
  • Bleeding involving the gastrointestinal tract




You will need to give a thorough history of your cat’s health and onset of symptoms. The history you provide may give your veterinarian clues as to which organs are causing secondary symptoms. Along with a thorough physical examination, your veterinarian will also conduct a thorough ophthalmological examination on your cat, if the eyes are showing symptoms of a diseased state.

Symptoms for multiple myeloma resemble those of several other diseases. Your veterinarian will need to rule out a number of other possibilities for the symptoms, such as infections, other types of tumors, and immune-mediated illnesses. To do that, your doctor will conduct a complete blood profile, including a chemical blood profile, a complete blood count, and a urinalysis. Diagnostic imaging will include X-rays of the vertebra and limbs to look for bone lesions, and ultrasound to examine the internal organs.


Your veterinarian may need to refer you to a veterinary oncologist for the latest information regarding treatment of this disease. Your cat may be hospitalized if there are high levels of urea - waste products and calcium in the blood. Also, if there is a bleeding disorder, or a significant bacterial infection, hospitalization may be required. A blood-cleansing procedure may be used, or blood may be withdrawn and replaced with an equal volume of fluids.

If possible, radiation therapy may be used on isolated areas, with the goal of curing the disease, or only to control signs and improve your cat’s condition. If there is a concurrent bacterial infection, it will be treated aggressively with antibiotics.

If your cat is being treated with radiation or chemical therapy, it will also need to be guarded against opportunistic infections that can result from the expected lowered immune response (known as immune compromised – a result of the treatment that is used to stop the growth of cancerous cells in the body). You will need to take care to prevent bacterial infections from occurring, such as those caused by puncture wounds from dog or cat fights. Dietary changes will be necessary if your cat is in kidney failure. Affected areas that are nonresponsive to chemotherapy, or single, solitary lesions may be removed surgically.

Living and Management

Your veterinarian will want to do a complete blood count and platelet count weekly for at least four weeks to assess bone-marrow response to the chemotherapeutic drugs. Blood tests with abnormal results will be repeated monthly to evaluate response to the treatment.

Protein analyses of the blood will be done monthly for several months until normal protein patterns are obtained. Once protein patterns have stabilized, monitoring will be periodically performed for signs of relapse. Abnormal skeletal X-rays should be repeated monthly every other month until they appear normal, and to evaluate your cat’s response to treatment.

Chemotherapy is intended to improve your cat’s condition, not to cure the multiple myeloma, but long remissions are possible. Relapse is an expected occurrence. The drugs that are being used will determine the side effects. Your veterinarian will go over what to expect, based on the types of drugs that are prescribed for treatment. Most patients develop mild low white-blood cell counts (leukopenia) during chemotherapy.

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