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What! Cancer! I thought it was an insect bite!

What is a mast cell?

A mast cell is a white blood cell found in many body tissues. Mast cells are allergy cells and play a role in the allergic response. When exposed to allergens (substances that stimulate allergies), mast cells release chemicals and compounds, a process called degranulation.

One of these compounds is histamine. Histamine is commonly known for causing itchiness, sneezing, and runny eyes and nose – the common symptoms of allergies.

What is a mast cell tumor?

A mast cell tumor (MCT) is a type of tumor consisting of mast cells. Mast cell tumors most commonly form nodules or masses in the skin; they can also affect other areas of the body, including the spleen, liver, intestine, and bone marrow. Mast cell tumors (MCT) are the most common skin. Most dogs with MCT (60-70%) only develop one tumor.

What are the signs that a dog may have a mast cell tumor?

Mast cell tumors of the skin can occur anywhere on the body and vary in appearance. They can be a raised lump or bump on or just under the skin and may be red, ulcerated, or swollen.

Mast Cell Tumors are 'The Great Pretender'

While some may be present for many months without growing much, others can appear suddenly and proliferate. Sometimes they can suddenly overgrow after months of no change. They may appear to fluctuate, getting larger or smaller even daily. This can occur spontaneously or with the agitation of the tumor, which causes degranulation and subsequent swelling of the surrounding tissue.

Caregiving Caution: Do not manipulate (feel) the tumor. MCT cells are prone to releasing histamine. In cases of excessive release, it can cause anaphylaxis shock, a life-threatening reaction.

How does this cancer typically progress?

MCT behavior is complex and depends on many factors. Typically, the pathologist can grade cell replication aggressiveness under a microscope on several criteria. MCT tumor grades are from I-III, with grade I being the least aggressive and less likely to spread if surgically removed early on.

Pet parent takeaway

By its appearance, there is no way to tell if your dog has a mast cell tumor. In veterinary medicine, mast cell tumors are known for their unpredictable appearance. They can look like something harmless, even in their most life-threatening forms.

Mast cell tumors are the second most common cancerous tumor seen in dogs. They account for 16-20% of all tumors. And the effects of even the tiniest mast cell tumors can be a matter of life and death. These tumors have the potential to spread throughout the body at high speed. And once they spread, they have the potential to destroy the body.

Despite the range in behavior and prognoses, MCTs are one of the most treatable types of cancer. The higher-grade tumors can be more challenging to treat, but the lower-grade tumors are relatively simple.

As with all cancers, early detection offers the best opportunity for survival and many years of companionship.

Living Grace Canine Ranch MCT Residents

Since 2020, Joey and Hemi have been ranch residents enjoying a protected and loved life. True to MCT research, neither has a remarkable medical history not shared by aging canines. Yet, recently both were diagnosed with MCT that seemed to appear out of 'nowhere.'

Whereas Hemi's tumor is small and located for surgical removal ease, Joey's MCT is a grade III and inoperable unless the cancerous mass can be shrunken through steroids.

Most likely, our caregiving role for Joey over the next four-six months will be offering palliative therapies to ensure his life journey is a joy-filled experience.

If you wish to sponsor Joey or Hemi's MCT treatment with a monthly gift, we are grateful for your generosity and compassion.

Please follow this link to donate to the medical treatment benefit of a Sanctuary Sweetheart.

Come to me, all you who are weary and burdened, and I will give you rest.

Matthew 11:28


Mast Cell Tumors/


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