Mast Cell Tumours; Who, When, Where?

Introduction
Mast cell tumours (MCTs) account for up to 21% of all skin tumours in dogs. They are known as round cell tumours, along with lymphosarcoma, histiocytoma and transmissible venereal tumour. The behaviour of the different histologic types of round cell tumour can be quite distinct, hence each histologic tumour type is treated differently.

Mast Cell Tumours and Surgery
Mast cell tumours arise in any location where normal mast cells are found. Particularly high concentrations are found in the lung, intestinal mucosa, perivascular regions and dermal epithelial surfaces where they have a role in the host defence mechanism. Secretory granules filled with biologically active substances such as histamine, heparin and serotonin give MCTs many of their unique histological and biological characteristics.
Mast cell tumours present major challenges to the surgeon due to the necessity for removal of wide margins, and reported rates of local recurrence up to 50%.
A retrospective study of the MCTs in dogs was undertaken at the University Veterinary Centre, Sydney, to characterise the types of MCT, evaluate the success of surgery and identify variables that may be of use in predicting local recurrence and survival.

Statistics
Of the 56 dogs with MCT 18 (32.1%) were entire males, 10 (17.9%) were neutered males, 7 (12.5) were entire females and 21 (37.5%) were spayed females. No significant sex predilections were identified. The mean body weight was 26.2 kg (range 3 to 42kg). Median age at the time of surgery was nine years (range 1 to 13 years) in the 53 dogs in which it was recorded. Fifteen breeds were represented. Boxers (12 dogs), Australian cattle dogs (6 dogs) and Staffordshire bull terriers (5 dogs) were significantly over represented when compared to the study population (p < 0.001, 0.045 and 0.044, respectively). Boxers presented significantly younger than other breeds; the median age was 9 years (range 1 to 11) versus 10 years (range 4 to 13) for the rest of the dogs in the study p = 0.017). [...]