Early Symptoms, Diagnosis, Treatment, Prognosis, and Management Guide for Canine Plasmacytoma

Oncology/CancerDiseasesMeongsiljang Veterinary Advisory Board

Canine plasmacytoma is a tumor that occurs when plasma cells, which produce antibodies, proliferate abnormally. Let’s explore the symptoms, diagnosis, treatment options, and prognosis for each type, ranging from cutaneous plasmacytomas to multiple myeloma.

What is Canine Plasmacytoma?

A veterinarian palpating a mast cell tumor nodule on a puppy’s paw.

Canine plasma cell tumors are growths that form when plasma cells, which produce antibodies, proliferate abnormally. They can be broadly categorized into cutaneous plasma cell tumors, which are localized to the skin and mucous membranes, and multiple myeloma, a systemic condition affecting the bone marrow and internal organs. The key point is that the progression and prognosis vary significantly depending on the tumor’s location. Cutaneous plasma cell tumors generally have a favorable prognosis if completely removed surgically, whereas multiple myeloma requires more aggressive treatment due to its systemic impact. Because cure rates and prognostic outcomes depend on the tumor grade and the patient’s overall health, definitive predictions are difficult. Therefore, it’s important not to overlook any new lumps on your dog’s skin and to have them evaluated promptly.

Why Does Plasmacytoma Occur? — Causes and Risk Factors

The exact cause of plasmacytoma remains unclear. Plasma cells are a type of white blood cell responsible for immunity, specifically producing antibodies. It is believed that genetic changes or immune system abnormalities in these cells disrupt their normal growth regulation. While certain breeds are reported to be more frequently affected, there is still insufficient data to establish definitive breed-specific incidence rates or average age of onset. Generally, plasmacytoma tends to occur more commonly in middle-aged to senior dogs, and it is thought to result from a combination of genetic predisposition and aging. Because the precise risk factors require further research, it is difficult to make definitive statements at this time.

Checklist of Major Symptoms by Type

Skin lumps (pink nodules): Small, round bumps may appear on the toes, ears, lips, or around the eyes.

Oral lesions: Lumps may develop on the gums, tongue, or roof of the mouth, or there may be a sudden increase in drooling.

Limping: Tumors on the toes can make walking uncomfortable.

Lethargy and loss of appetite: Systemic symptoms may accompany visceral involvement or multiple myeloma.

Bone pain and fractures: As multiple myeloma progresses, bones weaken and may fracture even without significant trauma.

A worried pet owner looking on as their dog lies listlessly.

Go to the Vet Within 24 Hours If You See These Symptoms

If your pet is limping severely or you suspect a fracture without any obvious trauma, if extreme lethargy, vomiting, and diarrhea persist for more than three days, if there is a sudden significant increase or decrease in urine output, or if you notice bleeding in the mouth, you should visit a veterinary clinic immediately. These symptoms may indicate systemic involvement of multiple myeloma.

How Is Diagnosis Performed?

If there’s any suspicion, we start with a fine-needle aspiration cytology to collect cells. Once plasma cells are confirmed, a biopsy is performed for definitive diagnosis and to assess the malignancy grade. To determine whether it’s multiple myeloma, additional tests are needed, including blood tests (total protein and calcium levels), urinalysis, and bone radiographs. If systemic involvement is suspected, a bone marrow aspiration is also conducted to check for hematologic cancer infiltration. Because the treatment plan depends entirely on the test results, an accurate diagnosis is essential.

Treatment Methods by Type

Cutaneous and mucosal plasmacytoma: Surgical excision is the primary treatment. When removed with wide, clean margins, the risk of recurrence is generally low.

Extramedullary plasmacytoma (e.g., gastrointestinal tract, spleen): After surgical removal, radiation therapy may be added as an adjunctive treatment depending on the case.

Multiple myeloma: Because this is a systemic disease, chemotherapy is the cornerstone of treatment. The goal is long-term, stable disease management rather than a cure. The choice of drugs and expected response vary based on the patient’s stage and overall health, so it’s best to consult with a veterinary oncologist to determine the most appropriate plan.

It’s important to develop a treatment plan that takes into account your pet’s age, overall health, and your household circumstances, in close collaboration with your veterinarian.

A puppy being prepped for surgery on the examination table at the animal hospital, alongside the veterinarian

Home Care and Management Points

Your pet should wear an Elizabethan collar for two weeks after surgery to prevent licking the wound. Contact the clinic immediately if the incision becomes red or starts draining. Because chemotherapy lowers immunity, it’s best to minimize contact with unfamiliar dogs and people. Since chemotherapy drugs are excreted in urine and feces for about 48 hours, always wear gloves when handling your pet’s waste. Consistent follow-up exams every one to three months are essential for early detection of recurrence.

A guardian staying by the side of a puppy recovering at home while wearing a neck collar after surgery

Breed-Specific Precautions and Recurrence Prevention

Plasmacytomas tend to be reported more frequently in certain breeds and in middle-aged to senior dogs. However, since breed-specific incidence rates have not yet been firmly established, please treat this information as a general reference. For senior dogs, even if no specific symptoms are present, ask your veterinarian to thoroughly examine the entire skin surface and the oral cavity during routine health checkups. Because cutaneous plasmacytomas can recur at the same site or in other areas even after removal, it is safest to maintain consistent follow-up monitoring over a period of time.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Is surgery always necessary for a plasmacytoma on the skin?

Yes, surgery is generally recommended. Even if the mass appears small, it’s essential to confirm whether it’s malignant, so complete removal along with a biopsy is necessary. The prognosis after surgery is usually good, so there’s no need for excessive worry.

Is plasmacytoma a type of cancer?

Plasmacytomas are tumors caused by the abnormal proliferation of plasma cells, so they are broadly classified as neoplasms (cancer). However, most cutaneous plasmacytomas are low-grade malignancies with a good prognosis following surgical removal. In contrast, multiple myeloma is classified as a blood cancer and requires more aggressive treatment.

What should I be careful about at home during cancer treatment?

Chemotherapy drugs are excreted in urine and feces for about 48 hours. Always wear gloves when handling waste, and dispose of soiled pads in sealed bags. For safety, wash your pet’s food and water bowls separately.

What should I do if it comes back?

If a cutaneous plasmacytoma recurs in the same location, repeat surgery is an option. However, if the tumor has spread to other areas or progressed to multiple myeloma, you should consult with a veterinary oncologist to discuss chemotherapy options.

Is there a way to prevent plasma cell tumors?

There is currently no clear method of prevention. Regular health check-ups and careful observation by pet owners are the best approach. Please show your veterinarian any new skin lesions or those that have persisted for more than a month without delay.

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References

[1] Moore A.R. (2023) Diagnosing multiple myeloma and related disorders. Vet Clin North Am Small Anim Pract 53(1):101–120.

[2] Vail D.M., Thamm D.H., Liptak J.M. Withrow & MacEwen's Small Animal Clinical Oncology, 6th Ed. Elsevier, 2019.

[3] Raskin R.E., Meyer D.J. Small Animal Cytologic Diagnosis: Canine and Feline Disease, 2nd Ed. Elsevier, 2016.

[4] Matus R.E. et al. (1986) Plasmacytoma in the dog: a retrospective study of 32 cases. J Am Vet Med Assoc 189(9):1091–1093.