Mast Cell Tumors: A Logical and Effective Approach

Introduction
Mast cells can be found throughout the body and play an important role in inflammatory reactions and aller- gies. Mast cells are filled with granules containing vaso-active mediators such as histamine, heparin etc. Mast cell tumours (MCT) occur everywhere in the body and are the most common skin tumours (16-20% of skin tumours) in the dog and second most common tumours in the cat. Most MCT are solitary but multiple MCT have been described. It is unclear at the moment if multiple MCT consists of metastases of one original tumour or of multiple solitary tumours. This review will evaluate the current scientific background of our knowledge about MCT.

Pathogenesis
The aetiology for MCT in dogs and cats is unknown, but a relation with chronic skin inflammation has been implicated. A link to C-reactive protein, a stimulator of the migration of mast cells to inflamed tissues during an acute-phase response may play a role. Mutation of c-KIT were found in MCT and a significant association was observed between the presence of a mutation and a higher grade of tumour. Another study showed a relationship between intron 11 deletion of c-KIT and the grade of MCT differentiation.

Clinical signs
MCT can vary in appearance but often present as raised cutaneous, hairless and often painless masses. Some MCT show obvious ulceration, others seem quite innocent. A history of increasing and decreasing size of the tumour is pathognomonic for this tumour type. Upon palpation, MCT may be soft (comparable to lipomas) or solid. Sometimes they appear well defined and sometimes ill defined with no obvious margins. An acute degranulation of and inflammatory reaction caused by a MCT is called Darier’s sign, which has been correlated with a negative prognosis. There seems to be no apparent breed or sex predilection, and the median age of dogs with MCT is between 9-11 years of age. Systemic MCT or mastocytosis has been described. These dogs will present with regional dissemination, oedema, ulceration, and abscessation (65% of dogs) or signs of systemic illness, including anorexia, vomiting, and diarrhoea (50%).  [...]