Cutaneous mast cell tumours in cats arise from the same immune cells (mast cells) as in dogs, but their behaviour is notably different. In cats, the majority of skin mast cell tumours are benign and are cured by surgical removal alone. Two main subtypes exist: the common mastocytic form, which appears as a solitary skin nodule and behaves benignly in most cases, and the less common histiocytic variant, seen predominantly in young Siamese cats. The histiocytic variant is particularly interesting because it often undergoes spontaneous regression — the tumours resolve on their own without treatment. This benign behaviour in cats stands in marked contrast to the often aggressive nature of mast cell tumours in dogs, highlighting how the same cell type can produce very different cancers across species.