Mast cell tumors are a type of cancer that originates from mast cells, which are a part of the immune system. These tumors can occur in various locations on the body, including the skin, and may appear as lumps or bumps. They are more common in certain dog breeds, such as Boxers and Bulldogs, but can affect any dog. The severity of mast cell tumors can vary widely. Some tumors are benign and can be easily removed, while others may be malignant and require more extensive treatment, such as surgery, chemotherapy, or radiation therapy. Early detection and treatment are crucial for a better prognosis.