The symptoms of mast cell tumors in dogs

Updated November 21, 2016

Mast cell tumours, which are common in older canines, are masses of cancerous cells. Although they are seen most in older dogs, dogs of any age and breed can develop mast cell tumours. Knowing the signs of a mast cell tumour can help you catch it as early as possible and seek the appropriate medical attention for your dog.


Mast cell tumours present as lumps under the skin of your dog. According to Kate Connick's Courteous Canines website, tumours are usually located on your dog's trunk, but they can be located elsewhere. The tumours themselves are groupings of cancerous cells that come together and form masses. Sometimes you will find one tumour and other times you will find multiple tumours grouped together.

Mast cell tumours have the ability to change size, sometimes from day to day, according to the Canine Cancer website. Most tumours are not painful, regardless of the size or changes that occur. However, from time to time, the mast cell tumours can become inflamed, causing pain to your dog. Occasionally, the pain is triggered by a histamine release that occurs when the tumours are touched, but they can be painful even without this histamine release.

Digestive Symptoms

Not every dog will develop the same set of symptoms with mast cell tumours or to the same degree. Yet, some dogs will develop digestive problems, which are a common symptom. Kate Connick's Courteous Canines points out that digestive problems are often linked to the location of the tumours. Tumours can cause your dog to develop abdominal pain, which can lead to diarrhoea and a loss of appetite. Sometimes a dog will vomit, and sometimes blood can be seen in the vomit. Blood is also common in the faeces of the dog. Bloody faeces present as dark or black faeces.

Other Symptoms

Depending on the location and the stage of the tumour, other symptoms can occur, according to Canine Cancer. For example, if the tumours are near the lungs, breathing problems or coughing can occur. Other common symptoms include bleeding problems, which lead to trouble with wound healing, swollen lymph nodes or high blood pressure.

Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author