The above picture shows Tigger (who is no longer with us) following the removal of his third and last tumor.
What are mast cells? Mast cells are a normal, white blood cell that forms in the bone marrow and matures in adjoining tissues. These cells produce chemicals, including histamine. Their purpose is to combine with other cells to fight invading material. They are important in fighting allergic responses, non-allergic skin diseases and assisting in wound healing.