Side effects
Does a tumour cause side effects?

Depending on the tumour location, it can cause troubles. For example, when a tumour invades organs or exerts pressure on organs. Moreover, malignant tumours can disturb the body simply by their presence. As the body fights the tumour this can lead to exaggerated reactions (also known as paraneoplastic syndrome). Certain of these reactions are listed below.


As a result of cancer wanting to eat less/ losing weight despite sufficient intake of nutrients. Many dogs lose their appetite due to the tumour, or they lose weight despite adequate nutrient intake because the tumour uses up all the energy. In the course of the disease, the fatty tissue is first broken down, but the muscles too, very quickly, in order to compensate for the energy deficit.

In this dog a demarcation of the dorsal vertebrae are visible due to the loss of muscles along the spine. On the head a demarcation of the skull is visible due to a loss of muscles.

Protein-Losing Enteropathy

The loss of proteins from the blood towards the feces can lead to a too low amount of proteins in the blood (when the loss is greater than the production). The cause is an increased permeability for blood proteins (due to damage of the intestinal wall, ulcers, blockage of lymph nodes).

Ulcers in the gastrointestinal tract

Can be the case with mastocytoma, gastrinoma

Too high level of calcium in the blood

A too high level of calcium in the blood (can be the case with ao lymphoma (10-36%), anal sac carcinoma (25%), thyroid carcinoma, multiple myeloma (20%), bone tumour, thymoma, squamous cell carcinoma, (adeno)carcinoma of the mammary gland, melanoma, primary tumour of the lungs, chronic lymphocytic leukemia, renal angiomyxoma, parathyroid tumour). An increase in blood calcium can have many causes (ao metastases towards the bone, an increased level of parathyroid hormones, … ) and can cause following symptoms:

  • Inability to concentrate urine
  • Residu of calcium salts in the kidney causing renal damage
  • Breakdown of the epithelium (lining) of the urinary tract
  • Drink and urinate a lot, which can lead to dehydration
  • Constipation, elevated blood pressure, involuntary muscle contractions, weakness, depression, vomiting, low cardiac rhythm, becoming slower, coma, death.
  1. anemia is associated with a chronic disease, it is often present when the tumour has metastasized. The cause is an anomaly in the organization of the iron stock and metabolism, a shorter lifespan of red blood cells and occasionally a decreased response from the bone marrow. The treatment consist of removing the tumour.
  2. immune-mediated anemia: in this situation the body attacks its own red blood cells. The treatment consist of removing the tumour or administrating an immunosuppressive dose of glucocorticoid (possibly azathioprine, cyclosporine, cyclophosphamide).
  3. blood loss: for example the case when ulcers are bleeding. The treatment consist of removing the tumour and a possible iron supplementation.
  4. microangiopathic hemolytic anemia: this is the consequence of blood destruction due to a deposit of fibrin and/or damage to the endothelium (damage to the lining of the blood vessels). In general, the cause is a formation of blood cloths that are disseminated throughout the blood vessels or damage to the blood vessels due to a tumour of the blood vessels (hemangiosarcoma). The treatment consist of removing the tumour and supportive care (administration of liquids, substances against nausea, … ).

A tumour can produce substances that have an effect on normal tissues. When too much of these substances (cytokines (IL-1, IL-6, TNFα, IFN), pyretic prostaglandins) are produced, the dog can become very sick and have a fever.

When a fever is present, it is important to check for the presence of an infection.

  • Cancer + fever + a lack of neutrophils (certain type of white blood cells) should be treated as an emergency.
  • Cancer + fever + no lack of neutrophils : must be followed up and the possible cause of an infection/inflammation.
  1. Bergman PJ. Paraneoplastic Syndromes. Withrow and MacEwen's Small Animal Clinical Oncology, 5th edition, Chapter 5 (p 83-92).