Mast cell tumors are the most common malignant skin tumor in dogs, but early detection and appropriate surgical treatment of low-grade tumors offers excellent long-term outcomes and quality of life.
Mast cell tumor welfare is significantly affected by early versus late detection: a low-grade MCT found as a small skin lump and excised with adequate margins has an excellent prognosis with minimal treatment-related welfare impact. The same tumor found after months of owner observation 'to see if it changes' may have progressed, spread to lymph nodes, or become a large, adherent mass requiring more extensive surgery and adjuvant therapy. The challenge is that MCTs are highly variable in appearance - they can look like any skin lump, leading to both over-anxiety about benign lumps and under-reaction to MCTs. The principle 'any new lump on a dog should be assessed by a vet' is a welfare-positive norm that catches MCTs early. Fine needle aspirate cytology is a simple, minimally invasive technique that provides immediate information about tumor cell type and guides management decisions.