Mast cell tumors are the most common skin tumor in dogs, with welfare implications ranging from minor for low-grade tumors to significant for aggressive high-grade disease requiring systemic treatment.
Welfare implications of mast cell tumors vary significantly with tumor grade and location. Low-grade tumors causing minimal local signs that are surgically removed carry low welfare cost. High-grade mast cell tumors that degranulate can cause local tissue reaction, gastrointestinal signs from histamine release, and systemic anaphylactic-type reactions that cause acute and severe welfare compromise. Chemotherapy and targeted therapy for advanced disease cause side effects including gastrointestinal disturbance, fatigue, and immune suppression that require careful welfare monitoring. The unpredictable nature of mast cell tumors makes quality-of-life assessment throughout treatment essential.