Mast cell tumour / Mastocytoma | Edek

Edek’s story

Mast cell tumours (mastocytomas) are among the most common skin tumours in dogs and the second most common skin tumours in cats. Their inconspicuous appearance can easily mislead pet owners, and a mastocytoma left untreated for a long time can lead to generalised mastocytosis.

What is mastocytosis? Mastocytosis is a very broad term meaning an excessive number of mast cells (mastocytes) accumulating in the body’s tissues. In the simplest terms, we can divide it into a cutaneous and subcutaneous form, in which mast cells accumulate in the skin or subcutaneous tissue but are not present in large numbers in other tissues, and systemic mastocytosis, in which mast cells accumulate in internal organs or the bone marrow. Systemic mastocytosis is very dangerous for our patients, so in such cases oncological care focuses on protecting patients from developing the systemic form. 

Edek’s case was a very rare form of mucosal mastocytoma – the tumour was located at the base of the tongue, causing swelling around the salivary glands and the mandible. At first the tumour appeared inoperable, but chemotherapy with vinblastine considerably reduced its size and made surgery possible. 

After surgery and chemotherapy, Edek is in good health.

Mast cell tumour in dogs – symptoms, diagnosis and treatment

A mast cell tumour is sometimes called “the great imitator” – it can look like a wart, a lipoma, an insect bite or a harmless lump. Typically, it can change in size and become red and swollen after being pressed or scratched. This is caused by the release of histamine from mast cells. Histamine can also cause ulcers in the stomach and duodenum – you can read more in the FAQ.

Breeds affected more often include boxers, pugs, Labradors and golden retrievers. Forms that develop on mucous membranes – as in Edek’s case – are rare and often have a more aggressive course than skin tumours.

Diagnosis

A mastocytoma can usually be diagnosed already on cytology. Before treatment, the neighbouring lymph nodes are assessed and – depending on the situation – the spleen and liver are examined by ultrasound. Histopathology of the removed tumour determines its grade, and testing for c-KIT gene mutations helps in choosing treatment.

Treatment

• surgery with an adequate margin of healthy tissue – the mainstay of treatment,
• radiotherapy or electrochemotherapy – when the tumour has been incompletely removed or when surgery is difficult,
• chemotherapy (e.g. vinblastine) and targeted drugs – for high-grade tumours, metastases or, as in Edek’s case, to shrink the tumour before surgery,
• antihistamines and stomach-protecting drugs – to limit the effects of histamine release.