Plasmacytomas In Dogs – Symptoms, Causes, & Diagnosis

Plasmacytoma (plasma cell dyscrasia) is a typical plasma cell malignancy that develops in the bone marrow (medullary, solitary osseous plasmacytoma (SOP) or soft tissues (extramedullary) as discrete, solitary mass or in clumps without any indication of systemic illness.

This plasma cell dyscrasia is a monoclonal proliferation of plasma cells and it is speculated to be an intermediary phase between clinically asymptomatic, premalignant monoclonal gammopathy (MGUS) and symptomatic plasma cell myeloma (multiple myeloma).

Solitary osseous plasmacytoma (SOP) is rarely reported in dogs. Reported sites include the zygomatic arch, ribs, and vertebrae.

When the tumor is confined to bone, it is called a solitary plasmacytoma (intramedullary plasmacytoma). However, if it is a present outside bone in soft tissues, it is referred to as solitary extramedullary plasmacytoma. In most cases after local tumor development, SOP eventually progresses to multiple myeloma. Dogs with solitary bone plasmacytoma have a higher progression rate to multiple myeloma when compared to extramedullary plasmacytoma.

Extramedullary plasmacytomas (EMPs) count for about 2% of all neoplasia in dogs. EMP can happen anywhere in the body with almost 90% in the head, aerodigestive tract, mainly in the oral cavity, paranasal sinuses, tonsillar fossa, and nasal cavity. EMPs occur most commonly in middle-aged to old dogs (> 8 years).

Solitary Osseous Plasmacytoma:

• Lameness
• Bone pain
• Pathologic fracture
• Paresis or paralysis
• Vertebral lesions
• Spinal cord compression

Extramedullary Plasmacytomas:

• Visible tumor mass (smooth, raised, red nodules).
• Polypoid, ulcerated tumors
• Oral bleeding
• Tenesmus
• Rectal prolapse/rectal bleeding
• Hematochezia
• Dysphonia
• Dyspnea

Treatment protocol for canine plasmacytoma is directed towards controlling the local tumor and tackling the concern for metastasis.

When your dog is diagnosed with plasmacytoma- your vet may recommend surgical removal, radiation, chemotherapy, or a combination of these treatments.

For local control, the most common options implemented are surgery and/or radiation therapy.

Plasmacytomas are often resistant to chemotherapy, and there are typically no durable responses.

However, Chemotherapy is usually set aside as a rescue choice for tumors that have started to metastasize or recurred.

Complete tumor removal by surgical methods is typically not possible due to the location of some tumors.

Nevertheless, pet owners should understand that the tumor will relapse after some time.

Dog owners should consult with their veterinarian as soon as they notice the symptoms as some conditions can be very serious (and possibly fatal).

Prevention is not possible for Plasmacytomas. Treatment and survival rates vary depending on the grade and stage of the neoplasm.

Good overall health and early detection are the only ways to prevent this condition.

Check your dog on a regular basis and consult your veterinarian immediately if you find any odd lumps or lesions.

Cocker Spaniel, Airedale Terrier, Kerry Blue Terrier, Scottish Terrier, Standard Poodle

1. Causes:

SOP: No definitive cause has been found.

EMPs: Viral infection, an overdose of irradiation, chemicals, chronic stimulation, and genetic disorders in the reticuloendothelial system.

2. Types:

Solitary osseous plasmacytoma (SOP): Also called Solitary plasmacytoma of bone (SPB), the most common form of plasmacytoma and originates in bone tissue.

1. The bone marrow involvement is minimal: Apart from the plasmacytoma itself, this type of SPB has clonal marrow cells less than 10%. MM rate of progression in 3 years is 20-60%.
2. No involvement of bone marrow: They are no clonal marrow cells apart from the plasmacytoma. MM rate of progression of this type in 3 years is 10%.

Extramedullary Plasmacytoma (EMP):

Also called extraosseous plasmacytoma, they are located at non-osseous sites with little or no bone marrow involvement. EMPs are classified according to the location: oral/ cutaneous and non-cutaneous. Cutaneous plasmacytoma is mostly found in older male dogs.

3. Morbidity:

SOP:

• Most cases of SOP reported in dogs ultimately progress to multiple myeloma.
• However, these dogs may have long disease-free intervals before disease progression.

EMP:

• They can originate from cutaneous or non-cutaneous
• The most common locations of plasmacytomas in dogs are the skin, oral cavity, eyes, ear pinnae, digits, larynx, trachea, stomach, spleen, rectum, and colon.

4. Mortality:

SOP progresses to multiple myeloma at a higher rate of progression than EMPs. Multiple myeloma is extremely fatal and with appropriate therapies, the dogs can live another 15-18 months.

5. Diagnosis:

• Cytology or immunohistochemistry
• Skeletal Radiography
• Bone Marrow Aspiration
• Serum Protein Electrophoresis

6. Differential Diagnosis:

• Multiple Myeloma (MM)
• Non-Hodgkin Lymphoma (NHL)
• Reactive Plasmacytosis
• Plasmablastic Lymphoma

7. Prognosis:

When detected early and with appropriate treatments, the dog’s prognosis is usually good.

EMP has a low metastatic rate and carries a favorable prognosis. Surgical removal is curative (almost 95%) for canine cutaneous and mucocutaneous EMPs.

Dog treated with both surgery and systemic chemotherapy for SOPs can have extended survival times.

The reasons for poor prognosis are progression to MM, new bone lesions formation with MM, local recurrence, local lymph node metastasis, and incomplete resection with functional damage.

Contact your vet right away, if you notice any of the following:

• Visible Tumor Mass (smooth, raised, red nodules).
• Lameness
• Paralysis
• If your dog blinks excessively or the eyes look painful and red continuously.
• Watery discharge/ Excessive tearing

The diet should be included foods containing high bioavailable proteins, good fats (including omega-3 fatty acids), vitamins A, and C, omega-3 fatty acids, zinc, and carotenoids.

• Fresh, organic meats, either raw or cooked, Eggs.
• You can also pick seafood over the usual beef and chicken.
• Omega-3 oily fishes such as salmon, tuna, cod, etc.
• Leafy greens such as spinach, kale, watercress, etc.
• Nonmeat/plant protein sources such as Nuts, Lentils, Beans, Eggs, etc.
• Citrus fruits or juices.
• Sweet potatoes, Tomatoes, Pumpkin.
• Pork, Tuna, Oysters.
• Blueberries, Broccoli, Cabbage, Carrots.

Response and prognosis are a direct correlation to the degree of the spread. Plasmacytoma's long-term prognosis is guarded as treatment depends on the location it is developed, but it is usually manageable. Remissions may occur and this is completely dependent on metastasis and the severity of the disease.