Mast cells are a type of cell widely distributed in the body and help in the normal immune response.
Mast cell tumours commonly affect the skin, the spleen (in the abdomen) and/or the intestines. The skin is the most common site for mast cell tumours in cats.
Cutaneous (skin) mast cell tumours most commonly affect the head and neck and affected cats develop one or multiple nodules or plaques in the skin. These may ulcerate. One form of cutaneous mast cell tumour is commonly seen in young cats (most commonly in Siamese cats) and this form spontaneously regresses over 6-24 months. However the other form is more commonly seen in older cats and can vary from being relatively benign to being an aggressive form of tumour with local invasion and spread (metastases).
Intestinal mast cell tumours are relatively uncommon, but are the third most frequent tumour affecting the intestines of cats (lymphoma and adenocarcinomas are much more common). In the intestine, these tumours tend to be highly aggressive and are seen mainly in older cats – spread (metastases) to local lymph nodes and more distant sites is extremely common. Clinical signs are often due to partial obstruction of the intestine.
With splenic mast cell tumours, commonly other sites are affected also (including lymph nodes, liver and sometimes even the skin). Loss of appetite, weight loss and vomiting are common signs.
Mast cell tumours can be removed surgically. This may be curative for many low grade skin mast cell tumours, but the prognosis is much more guarded where there are metastases and with intestinal or splenic mast cell tumours. If there is splenic involvement removal of the spleen may be helpful and, even in the presence of metastases, can produce good improvement for around 12 months in many cats.