On average, dogs get mast cell tumors at about 7-8 years of age.
A dogs mast cell tumors can be loosely described as looking like a pencil eraser growing on or just below the surface of the skin. They can grow singly or in groups. Not all mast cell tumors are malignant, some 2/3 of them are actually benign, harmless growths.
If a dogs mast cell tumor grows larger than an inch, it should be considered cancerous. But don't try to figure that out yourself, a visit to your veterinarian should be in order to find out.
Mast cell tumors are typically treated with surgical removal. More in depth treatment may be necessary if the growth is cancerous and it has spread throughout the body.