Diseases and conditions image
Diseases and conditions image EquiMed


Also known as

Cutaneous mastocytoma, mastocytosis, mast cell tumors


Mastocytoma is seen only rarely in cattle. It may appear suddenly as one rapidly-growing nodule within the layers of the skin, which may spread widely if traumatized, or may appear as multiple tumors from the beginning.

This disease involves mast cells, which are the master regulators of the immune system. They originate in bone marrow and go to all tissues of the body. Each mast cell contains storage sacs (granules) containing powerful biologically active molecules called mediators that can be secreted when mast cells are triggered, leading to allergic and inflammatory diseases.

Most of these cells are located in connective tissues, at boundaries between the tissues and the outside environment such as at the mucosal surfaces of the gut (lining of the stomach and intestines) and the lungs, and in the skin. They play an important role in helping defend these tissues from disease.

By releasing chemical alarms such as histamine, mast cells attract other players of the immune defense system to areas of the body where needed. Thus they serve as immune sentinel cells to respond directly to pathogens and also to send signals to other tissues to control and harmonize immune responses. Mast cells play a pivotal role in defense against pathogens, and mediate inflammatory responses such as hypersensitivity and allergic reactions. Upon stimulation by an allergen, the mast cells release the contents of their granules (a process called degranulation) into the surrounding tissues.

The term mastocytosis is often used for spontaneous mast-cell disease in a variety of species, including humans. Mastocytosis is most common in the dog and much less common in humans, cats and cattle. One manifestation of this disease is a mast cell tumor consisting of mast cells. Mast cell tumors most commonly form nodules or masses in the skin, but they can also affect other areas of the body, including the spleen, liver, intestine, and bone marrow.

In humans they usually occur as benign, solitary masses on the skin of the head, neck, trunk, and legs. In pigs and cattle, mast cell tumors are less common. They tend to be solitary and benign in pigs and multiple and malignant in cattle.

Mast cell tumors in cattle often involve the skin. Age of affected cattle ranges from 2 months to 12 years. Holstein and Holstein crosses may be predisposed to develop cutaneous mast cell tumors. Congenital systemic mastocytoma with multiple skin nodules has been seen in a stillborn Holstein calf.

Mast cell tumors in the skin of cattle can be single or multiple. These tumors are raised, firm, tan nodular masses that may become ulcerated. Tumors may have well-defined margins or they may be infiltrative—moving into the surrounding tissue.


  •     Firm nodules in the skin that may become ulcerated


This disease is due to a malfunction of mast cells. These are long-lived tissue-resident cells with an important role in many inflammatory settings, helping provide a defense against pathogens and parasites. They also play a role in allergic reactions.

Sometimes mast cells become defective and release mediators because of abnormal internal signals. Certain mutations in mast cells can produce populations of identical mast cells – called clones – that overproduce and spontaneously release mediators. These abnormal cells can grow uncontrollably and are unusually sensitive to activation in a condition called mastocytosis.

Mastocytosis (when the body produces too many mast cells) can affect skin and internal organs such as the bone marrow, gastrointestinal tract, liver, and spleen. Most human patients or animals with mastocytosis have cutaneous (skin) tumors or benign systemic forms, but aggressive disease can also occur.

Cutaneous mast cell tumors in cattle are associated with a relatively high rate of metastasis. Spread to lung and lymph node is most common, and metastasis to liver and muscle has also been reported.


There is no way to predict or prevent this condition


Surgical removal (making sure that all tissue around the tumor is removed) is the usual treatment for the skin tumors in all species, but with guarded prognosis following excision of these mast cell tumors in cattle.

About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.