Metastatic Cancer in Cats

Metastatic cancer is cancer that has spread from the organ where it originated to other organs. Cancer cells, unlike normal cells, don’t stick to similar cells. Rather, they break away from the tumor first formed and travel through the blood stream or through the lymphatic system to other parts of the body and form new tumors in those parts. This new tumor is called a metastatic tumor.

Metastatic Tumors

The cells of metastatic tumors come from the original tumor. Thus, if the original tumor was formed in the lungs and the metastatic tumor was formed in the liver, the metastatic tumor would have cancerous lung cells. The cancer in the liver would thus be metastatic lung cancer and not metastatic liver cancer. Although cancer cells have the ability to metastasize to any part of the body, metastatic lung cancer, metastatic liver cancer and metastatic bone cancer are more common. The effect of the cancer on the cat will depend on the location and spread of the primary and metastatic tumors.


The symptoms of metastatic tumors will depend on the site to which the tumor has metastasized. The symptoms in metastasized bone cancer are bone fractures and pain while the symptoms of metastasized liver cancer include jaundice and swelling in the abdomen. Pets suffering from metastasized brain cancer exhibit symptoms of seizures and neurological disorders. Often, the primary tumor is detected only after symptoms of the metastasized cancer start appearing.

Symptoms Common to Metastatic Cancers Include:

  • Loss of weight and appetite
  • Lumps or small bumps under the skin
  • Behavior change
  • Gastrointestinal disorders
  • Weakness
  • Sores that don’t heal


Some of the tests recommended by the vet to identify the type of cancer present are blood tests for complete blood count, X-rays, physical examination of the cat, analysis of the urine, abdominal ultrasound and biopsy. Biopsy for metastatic cancer involves the removal of the cells from the tumor to examine them for their grade and origin. It’s sometimes possible to tell whether the tumor is a primary tumor or a metastatic tumor as a metastatic tumor will appear similar to the organ from which it has metastasized. However, sometimes it’s not possible to determine where the primary tumor is situated and such a primary tumor is known as cancer of unknown primary origin.


If metastatic cancer is diagnosed, prognosis is not favorable. Chemotherapy is not very effective but might help to slow the progression of the disease. Cats tolerate chemotherapy well but do suffer side effects like vomiting, diarrhea, hair loss and loss of appetite. Surgery is also not very effective as all the affected cells can’t be removed because of the metastasis. Radiation is another option. Since radiation damages rapidly dividing cancer cells, such cells no longer divide and spread, and eventually die. This helps to slow down the progression of the cancer. Although radiation is effective in some cancers, other cancers may be resistant to it.

Early detection of cancer, particularly before it metastasizes, increases the chance of successful treatment. It’s best to seek medical care as early as possible to give pets a fighting chance in their battle against cancer.