Mucocutaneous Plasmacytoma in Cats

Mucocutaneous plasmacytoma is a type of rapidly growing tumor affecting plasma cells. These cells are a form of white blood cells that secrete a large amount of antibodies. Mucocutaneous plasmacytoma specifically affects plasma cells around the skin area. These tumors are typically found on the legs and trunk, or body, of your cat and can be malignant (cancerous) or benign.

Symptoms of mucocutaneous plasmacytoma can begin subtly. This type of tumor tends to grow rapidly, and tumors will quickly become plainly visible to observant pet owners. Symptoms may include:

• Hair Loss
• Lightening of skin
• Raised growth underneath skin
• Tumors located on trunk or legs
• Tumors also rarely located on feet, lips, ears or in the mouth

In the event that the tumor is cancerous, additional symptoms may develop if the cancer metastasizes, or spreads to other parts of the body. These may include:

• Lethargy
• Weakness 
• Depression 
• Loss of appetite

All tumor growth begins with unnatural cell mutation. In mucocutaneous plasmacytoma, the plasma cells which are responsible for forming white blood cells and antibodies will mutate rapidly. This unnatural growth causes a large mass to form which can grow in size until it affects other bodily systems. In cancerous cases, the damaged cells can migrate to nearby lymph nodes or other bodily organs and cause healthy cells in these systems to mutate unnaturally.

The cause of this mutation is unknown. Many scientific studies focus on environmental factors or exposures to known carcinogens. 

In order to diagnose mucocutaneous plasmacytoma in your cat, your veterinarian will need to begin with a complete medical and physical history of your cat. You should provide a timeline of symptoms and appearance of any lumps or bumps on your cat. The date of first appearance, and relative growth since then, will be especially important in determining rate of growth and potential treatment options. Appearance of any other symptoms will also help identify whether the tumor is cancerous and whether it has metastasized to other parts of the body.

Your vet will also conduct their own thorough physical exam. During this exam the veterinarian will locate any tumors and will document their location and size. Your veterinarian will also manually palpate your cat’s lymph nodes. Lymph node involvement near the location of the tumor may indicate the presence of cancer. 

Finally, your vet will conduct a needle aspiration of the tumor. This is the definitive diagnostic tool for determining whether the tumor is malignant. This procedure involves inserting a fine needle into the tumor and extracting a small amount of tissue cells. This sample is sent off to a laboratory where they will conduct an analysis to identify the presence of any abnormally affected cancer cells. Given the location of mucocutaneous plasmacytoma near the surface of the skin, your cat will generally not need to be anesthetized for this procedure. From needle insertion to tissue extraction, the entire needle biopsy typically will only take a few minutes.

The typical treatment of mucocutaneous plasmacytoma, regardless of malignancy, is typically surgical removal. Your cat will need to be admitted to the veterinarian’s office. The vet will conduct pre-surgical tests such as x-rays and a full panel of bloodwork. The x-ray will help pinpoint the location of the tumor. The blood panel will help identify any underlying abnormalities which may add extra risk to the procedure or identify the presence of any additional or underlying conditions. 

During the surgery, your vet will attempt to remove the entire tumor. Given the nature of these types of growths, it will be important for your vet to remove all of the mutated tissue. This is called “getting clean margins”. If clean margins, free of mutated cells, are not obtained, there is a high likelihood that the cancerous tumor will return.

In the case the mucocutaneous plasmacytoma is malignant, your veterinarian may discuss alternative or additional treatment options. Depending on location and size of the tumor, these treatment options may include radiation or chemotherapy.

As with any surgical procedure, if your cat’s mucocutaneous plasmacytoma has been removed via excision you will need to closely follow your vet’s post-surgical instructions. You will need to keep your cat quiet and calm and closely follow any medication protocol to protect against postoperative infection. You will also need to follow up for removal of sutures and, in the long term, for physical examination for the appearance of any additional tumors.

In the case of non-malignant mucocutaneous plasmacytoma, prognosis for long term recovery for your cat is good as long as the entirety of the tumor is removed via surgical excision. These types of tumors do not have a tendency to regrow or appear on alternate parts of your cat. With proper care and follow up vet visits, your cat can live a long, healthy life after treatment for mucocutaneous plasmacytoma.