Cutaneous mast cell tumours are very common in dogs, often presenting a diagnostic dilemma, with many tumours showing aggressive biological behaviours. Cutaneous mast cell tumours are less common in cats; however, when they do present, they most commonly exhibit benign biological behaviour, so complete excision of the mass is usually curative. Cutaneous mast cell tumours have been reported in several other species as diverse as horses and tortoises. But did you know that cutaneous mast cell tumours are one of the most common skin tumours in domestic ferrets (Mustela putorius furo)?