All mast cells require a tyrosine kinase receptor called c-kit, (also known as stem cell factor (SCF) receptor), which is a protein on the membrane of the cell, to survive. SCF is a growth factor for blood cells and therefore stimulates production of various types of blood cells. In some mast cell tumors, a mutation in the gene that codes for the c-kit receptor can occur that results in production of a receptor that is always activated which can result in mast cell tumors developing in dogs. Currently you can find testing options for the most common exon 11, but also testing options that include multiple exons: 11, 8, 9, 17. You can view exon/mutation information under phenes C-Kit 8, C-Kit 9, and C-Kit 17