dog plasmacytomas information

Plasmacytoma Dog Tumors: Everything To Know

A plasmacytoma dog tumor crossed my path the way most lumps and bumps do: while I was petting my Cocker Spaniel. I immediately made an appointment for the veterinarian to aspirate the lump, and it was sent off to an outside lab. My vet thought it looked like a mast cell tumor, but it wound up being a unique cutaneous mass that had to be removed.

The 1-cm raised reddish lump on my Cocker’s left pinna near the external canal base of his ear was diagnosed as a plasmacytoma. Dog plasmacytomas, or plasma cell tumors, are round cell growths originating from lineages of B cells found in bone marrow, according to Adam Christman, DVM, MBA, Chief Veterinary Officer for dvm360.

They are most commonly found in or on the skin, most specifically on a dog’s head or limbs, including the paws and between or on the toes. They can also be located in a dog’s mouth, colon, or rectal regions. There are several types of canine plasmacytomas including benign plasma cell tumors, multiple myeloma, and single osseous plasmacytomas.

The prognosis is overall very good for extramedullary plasmacytomas, and the outcome of all three types depends on the staging, location, and if there is spread or metastases of malignant cells to other areas.

My dog’s plasmacytoma is the extramedullary type, and his veterinarian proposed a unique treatment plan aimed at destroying the plasma cells. I’ve interviewed other dog parents whose dogs have been diagnosed with plasmacytomas of different types and in different areas of the body.

In this article, I will share all three of our dogs’ journeys, what the experts have to say, what to do if your dog is diagnosed with a plasmacytoma, and some bonus information if you find a lump or bump on your dog.

dog plasmacytomas vet visit
Dexter at the vet visit.

What Are Plasmacytoma Dog Tumors?

Most canine plasmacytomas are discovered by accident. Pet parents are usually petting their pooch, running their fingers through his coat, examining the skin, and suddenly they feel or see a lump on the dog.

Veterinarians, even the most skilled and scholarly vets, cannot tell what a lump or bump is on your dog simply by looking at it or feeling (palpating) it. Fine-needle aspiration or biopsy is required to achieve a proper diagnosis.

Canine plasmacytomas occur when plasma cells in the immune system create antibodies that work against infection or infectious diseases. A plasmacytoma results when those plasma cells are disorganized and uncontrolled.

“Most plasmacytomas are benign (not malignant),” according to Dr. Christman. “They tend to hang out near the nail beds and in between the webbing of dogs’ toes.”

dog plasmacytoma on paw
Megan Danielle’s dog with a recurrent plasmacytoma of the paw.

There are three types of dog plasmacytomas:

Plasmacytoma TypeDescription
Extramedullary plasma cell tumorsGenerally found in the skin and oral cavity, such as the face, lip, and ear canals. However, they have been seen in the gastrointestinal tract, lymph nodes, and spleen. According to Kansas State University, “Oral plasmacytomas are biologically more aggressive than cutaneous counterparts and can undergo local invasion into the underlying bone, however a complete surgical excision of the mass results in only rare recurrence or metastasis.” They are generally solitary and do not spread. Dr. Christman reports they are generally benign but only a biopsy of some sort can confirm that.
Multiple myelomaThis type of plasmacytoma is usually a very malignant cancer. It may involve several organs and bones and cause pain to the dog. Dogs with multiple myeloma may have a certain type of protein in their urine. Without treatment, such as chemotherapy, and sometimes radiation, multiple myeloma can be fatal.
Solitary osseous plasmacytomaThough rare, they can affect any bone in the dog’s body. Long Island Vet Specialists say most dogs with a solitary osseous plasmacytoma will advance to multiple myeloma.

Once a dog is diagnosed with a plasmacytoma and the type is known, I would most definitely seek a veterinary oncologist for a solitary osseous plasmacytoma, multiple myeloma, or extramedullary plasma cell tumor (depending on its location).

They can confirm if the plasmacytoma is confined to a single location in the dog’s body.

What Are The Symptoms Of A Canine Plasmacytoma?

Most dog plasmacytomas that are diagnosed as extramedullary are discovered through palpation or seeing a new lump or bump on or in your dog’s skin or somewhere on his body. The mass is generally raised, red or pink, 1 to 2 centimeters at first, and may bleed.

For the more aggressive type of plasmacytoma, multiple myeloma, the Veterinary Information Network lists symptoms of fatigue, vomiting, loose stools, and lack of appetite. However, many other diseases and conditions may cause the same symptoms, which is why aspiration or biopsy of a lump is imperative for a proper and early diagnosis.

Solitary osseous plasmacytomas in dogs arise from bone. Thus, lameness and pain are potential symptoms. Diagnostic testing is imperative and a bone marrow aspiration, biopsy, radiographs, blood work, or other lab tests are usually performed on the dog.

Is A Canine Plasmacytoma A Type Of Cancer?

Plasmacytomas contain plasma cells and they can multiply and become abnormal and malignant. Not all plasmacytomas are cancer, as is the case with an extramedullary plasmacytoma. Dr. Christman says most plasmacytomas are benign, and the National Canine Cancer Foundation agrees, as multiple myeloma accounts for less than 1 percent of neoplasms in all animals.

Yes, plasmacytomas are a type of canine cancer but in most cases, Dr. Christman and other experts agree they are benign. If the cancer is advanced or spread to other organs, an oncologist should most definitely be involved in the dog’s care.

What Are The Common Places Canine Plasmacytomas Appear?

Extramedullary dog plasmacytomas occur in places like the skin or mucous membranes, including a dog’s mouth, gums, and lips. If the plasma cells are found in the bone marrow, this would be considered a medullary plasmacytoma.

“They tend to hang out near the nail beds and in between the webbing of dogs’ toes,” Dr. Christman notes. “In regions that don’t involve skin, this type of tumor can be found inside the dog’s mouth and colon regions.   Most of these tumors are solitary and less than one percent are associated with multiple myeloma (plasmacytoma arising IN the bone marrow).”

My 12-year-old Cocker Spaniel’s plasmacytoma showed up on his ear pinna near the external ear canal. Susan Thaw Greenberg’s dog, 10-year-old Woody, was diagnosed with a plasmacytoma in his mouth located between two of his lower jawline teeth.

Megan Danielle’s 12-year-old dog had surgery for a plasmacytoma on the bottom of her foot. A few months later, it grew back to almost twice the size and further intervention was warranted.

Are Certain Breeds More Prone To Plasmacytomas?

Although any dog can be affected by plasmacytomas, Dr. Christman says certain breeds are at greater risk. These include West Highland Terriers, Golden Retrievers, Labrador Retrievers, Standard Poodles, and Cocker Spaniels.

Extramedullary plasmacytomas comprise about 2.5 percent of all neoplasms in dogs and occur most commonly in middle-aged to older dogs (mean 8 to 10 years). Over at dvm360, they mention Boxers and Airedale Terriers as additional breeds of extramedullary plasmacytoma.

Solitary osseous plasmacytomas (SOP) are rarely reported in dogs and most cases progress to multiple myeloma months to years after local tumor development.

How Are Plasmacytoma Dog Tumors Diagnosed?

Cytology and immunochemistry are the two most commonly used tools for diagnosis and staging. Cytology involves cell analysis and immunochemistry uses antibodies to look for certain markers in a tissue sample.

If surgery is warranted, Dr. Christman says a biopsy is strongly advised to confirm the diagnosis and to ensure that all tumor cells have been surgically excised accordingly.

Susan Greenberg’s Cocker Spaniel, Woody, had a biopsy to confirm the diagnosis of extramedullary plasmacytoma. Susan took a photo of Woody and noticed a red spot on his gums.

After the diagnosis, Dr. Joseph Cyrus, an internal medicine specialist, aspirated Woody’s liver and spleen to be sure it had not spread throughout his lymphatic system. The aspirates were clean, his one enlarged lymph node was aspirated, it came back normal, and Woody did not have multiple myeloma.

Susan has peace of mind knowing the surgical margins are clean. If the margins around the plasmacytoma were not clean, further surgery would be required, as the cells could become malignant. Because Woody’s plasmacytoma was in his mouth, surgical removal was recommended.

Because my dog’s extramedullary plasmacytoma was located on his ear, his vet performed a fine-needle aspirate in the office and sent the samples out for laboratory diagnostics. She also gave him a shot of Benedryl in the event the lump was a mast cell tumor, as that would help calm the irritated lump. Dexter’s cytology report is shown below. Surgical excision was recommended.

diagnosis of plasmacytoma dog

In Dexter’s case, and with his history of a previous autoimmune disorder (IMT) and mitral valve disease, our vet suggested we do cryosurgery using super-cooled liquid nitrogen. Our veterinarian reminded us the ear has many blood vessels and Dexter would require general anesthesia for complete removal and to properly control bleeding. We discussed options and agreed on CryoProbe.

CrypoProbe was used during a subsequent visit after my dog received a local anesthetic to his ear. Cryotherapy is an excellent option for dogs who have certain types of lesions. I wanted to avoid general anesthesia, so we opted for freezing the lump. He was done in 15 minutes and there were no adverse side effects. Although our vet told us two CryoProbe sessions may be necessary, we stopped after one treatment.

dog plasmacytoma on ear
Dexter’s ear before CryoProbe, left, and several weeks after

The lump was frozen and, in the weeks, after, dead tissue slowly sloughed off. I kept it clean and had to apply an antibiotic powder to the area when it bled a bit. After a month, it didn’t seem to decrease in size and the vet felt a second treatment would not be effective. We talked about having it removed via laser surgery under twilight anesthesia in the future, but since that time, the lump has decreased significantly.

Cryotherapy has been shown to reduce the size of the growth (again, depending on location) but doesn’t necessarily completely remove the margins, according to Dr. Christman. This may be beneficial to pet parents with financial constraints for surgery and prepare a multimodal approach to therapy, including cryotherapy and medications. Due to the dead tissue sloughing off and entering Dexter’s ear canal, he developed an inner ear infection in the affected ear.

During a followup visit, we were prescribed an antibiotic powder called Neo-Predef . After 10 days of antibiotics and increasing my dog’s CBD oil, the lump suddenly decreased significantly.

dog plasmacytoma after treatment
The plasmacytoma in Dexter’s ear is almost gone.

What Is The Treatment For Canine Plasmacytomas?

Treatment for dog plasmacytomas varies. Sometimes, cryotherapy can be used. Dr. Christman reports they may not always need to be removed, as he has had personal success with canine clients using corticosteroids and an antibiotic, doxycycline. He says depending on the location, size, and tumor cell progress, these tumors can resolve on their own with aggressive medical therapy for four to six weeks and frequent rechecks with your veterinarian.

In many cases, surgical removal of skin and oral plasmacytomas is curative, but others may require treatment with chemotherapy, radiation, and/or medication.

If surgery is warranted, a biopsy is strongly advised to confirm the diagnosis and to ensure that all tumor cells have been surgically excised accordingly. Surgery may involve traditional excision under general anesthesia, the use of twilight anesthesia for local excision, cryotherapy, or laser surgery for extramedullary plasmacytomas of the skin.

In Woody’s case, Dr. Julius Liptak, an oncology surgeon and surgical specialist in small animal surgery, recommended a mini mandibulectomy, an operation for benign or low-grade oral tumors of the mouth. A small wedge was removed, which included the mass and two incisor teeth.

Preoperative and postoperative photos of dogs who underwent a unilateral rostral mandibulectomy can be seen here, with images of Woody’s pre- and postoperative photos below. The Merck Veterinary Manual reports when this type of tumor arises in the mouth, it tends to multiply.

dog plasmacytoma in mouth
Woody preoperatively.
dog postoperatively for removal of plasmacytoma
Woody postoperatively.

For solitary extramedullary dog plasmacytomas, dvm360 reports complete surgical removal is often curative. They say non-oral extramedullary plasmacytomas are more aggressive in behavior and dogs are often treated with surgery alone or surgery with additional therapies, such as medicine, chemotherapy, and/or radiation.

Dogs with more aggressive multiple myeloma should be under the care of a veterinary oncologist to discuss treatment options including, but not limited to, surgery, radiation, chemotherapy, and medication(s).

More Information On Canine Lumps And Bumps

I’ve been through most lumps and bumps on dogs over the past few decades, and I’ve learned a lot. Like people, no two dogs are alike and no two lumps are the same. Here are few articles I’ve written to help guide you in your knowledge of lumps and bumps on dogs.

Dog Parent Guide To Lumps On A Dog

Unexpected Warning Signs Of Dog Cancer

How To Treat And Prevent Lipomas In Dogs

Help For Dogs With Mast Cell Tumors

Has your dog ever been diagnosed with a plasmacytoma? Tell us in the comments below.

How are dog plasmacytomas treated


  1. Thank you! This article explained a lot to me about my dogs condition and options for treatment. I greatly appreciate the time you take to share this information with your readers.

  2. what was the final outcome from the dog that had it on his paw? that is what we are currently dealing with.

    1. We haven’t received any updates from her owner, but a plasmacytoma in that location most definitely needs to be removed. I would 100 percent see a specialist/oncologist or qualified surgical veterinarian for this.

  3. Can plasma cell tumors in the ear bleed enough to cause anemia? Could the bleeding be deep in ear canal and then re-absorb and the cycle continues

    1. I am not certain on that but anything that bled a lot I would have checked and ask my vet for sure.

  4. My border collie was diagnosed with plasmacytoma in the colon. After getting her groomed I noticed she has a growth on her leg that looks suspicious.

  5. Our Bagel is 14 and was diagnosed with this right after her mothers cancer finally did her in. Hers seems to be very fast growing, within weeks we finally had a good diagnosis but it was already wrapped around 4 ribs and her stomach a bit. We opted for palliative care due to the extensiveness of the cancer already and her age. It’s almost tripled in 5 weeks. We’ve done chemo pills but with no success. Is there anything else we should discuss with her oncologist in 1.5 weeks during her next appointment? What’s the usual life span when it’s growing like this?

    1. I dont have specific information on the typical life span. You are doing the right thing by working with an oncologist. I would ask the oncologist that question. However, dogs are amazing and resilient and some dogs last a long time. My heart is with you and for your sweet baby.

    2. Our Doberman was diagnosed with plasmacytoma in May 2021 it was located on his rear right inside toe. We had the toe amputated with clear margins. He was disease free for almost a year. At his relapse, he had multiple tumors on multiple extremities. He was started on melphalan. Unfortunately his disease progressed through the chemo. We were offered a second line chemo but the success rate of it was less than the first drug. My husband happens to be a medical oncologist and he and our veterinarian oncologist decided the side affects were not worth the odds of success. We are now about 6 months out from that decision and his disease has spread and his pain has increased. We know we are on borrowed time but until very recently he has had a very good quality of life.

  6. Our 10 year old Yorkie was diagnosed with Plasma Cell tumor in the bed of her right front paw last August, 2021. After it being excised we saw an Oncologist who asperated some fluid from the site and saw no cancer cells and margins were clear. This past week she was groomed and our groomer found two more. One in the left front paw and one in the bed of
    left rear paw. I saw her regular dr this morning. She aspirated some fluid and said cells look like Plasma Cell again. We have an appointment with the Oncologist Friday,April 1. I’m sure she’ll excise these and hopefully margins will be clear and no further treatment will be necessary. From everything I’ve read, these type of tumors are very common and it seems to be all about early detection. I feel good about my little one. She was groomed March 7th and they were not there, so she’s only had them surface in the last 3 weeks. Praying for a positive outcome.

    1. OOOH the paw is a very common area for these tumors. It sounds like you are on top of this. I am glad all has gone well. I wish you all the continued success with your baby.

  7. My old almost 16 year old dog has a Plasmacytoma tumor on his left front paw.. on the inside toe. Is there anyway to treat this other than removal. I would hate to have him lose a toe at this age.. afraid of putting him under and also of how hard this recovery would be for a dog of his advanced age.
    Please advise on other treatments.. just to make small and more comfortable for him to get around on.

    1. I would see a veterinary oncologist for options. Other than removal, I am not certain of other treatments. Perhaps you can ask if laser removal is an option? I am not certain because I know they want clean, large margins. All my best to you and your sweet senior, Nancy.

  8. Hi, my 6,5 year old mixed breed cocker spaniel was recently diagnosed with plasmocytoma. We found a little bump (not bigger than a tick) between in two middle fingers in a front paw. It was quickly removed and biopsy revealed the plasmocytoma. So far, the blood analysis seems to show no further spread (no protein peak). We asked for further advice to several vets and some are very positive, saying the prognosis should be very good with curative surgery, and two others, including the vet surgeon, are very pessimistic saying in two years max. he should be gone. We have planned another surgery to have larger clear margins and getting the removed material once more sent to the lab. Is the prognosis so bad? I am a bit confused since when I am doing researches in French, websites usually mention a quite negative outcome which seems different on websites in English.

  9. May 2021 our 6 year old Doberman was diagnosed with a plasmacytoma. It was right above the nail on his medial right rear toe. We elected to amputate the toe and got clean margins. March 2022 he developed another tumor. It was removed with clean margins and was a plasmacytoma as well. Before the stitches were out from that tumor, 2 more erupted. At this time he had elevated liver enzymes. He began oral melphelin. After 6 weeks of the chemo all existing tumors grew and he has approximately 8 new ones. One of the tumors has gotten large and is bleeding. His liver enzymes are still increasing. We are now faced with really tough decisions as his quality of life is starting to decline.

  10. 7 yr old cattle dog (in Australia) has sores all over his lower limbs and face – too many for surgery and they are like sores rather than lumps. My vet hasn’t seen it before. He is consulting w oncologist and on chemo but spreading still. Is it very painful do you know? Not wanting him to suffer – he’s a tough boy

  11. I’m so glad I found this post. Gumbo just had one of these removed, so I was googling to find out more info. Your blog post saved me all the work with all these sources linked like you always do. Thanks!

    Gumbo’s was on his gum on the outside of his bottom jaw. Just on the surface though and easily removed.

  12. Our 11 1/2 old Border Collie/Australian Sheppard dog has developed a spot on the underside of her tongue. It was aspirated and it was determined to be a non cancerous plasmacytoma. I have read that in most cases , as based on the location, that this is a non metastasized cancer. Has anyone experienced a similar situation? If yes what was the outcome and how did you handle the situation?

    1. As long as your dog is under the care of a veterinarian and they diagnosed not cancerous, I would keep an eye on it. You can always have a second opinion or have the biopsy and notes sent to an oncologist.

  13. Hi I just came across your post. My dog was diagnosed (via biopsy) with bilateral plasmacytomas in his ears, just like your dog. I’m trying very hard to find any specialist willing to excise these, or perform cryo or laser on them but I’m only getting recommendations of total ear canal ablations bilaterally… any recommendations. I really don’t want to move forward with such an invasive procedure

    1. Emily, My veterinarian was willing to do laser surgery and get clean margins and my dog’s plasmacytoma never came back. How big are your dog’s growths? Are they deep in the canal? TECA does seem extreme.

      1. Idk how deep but the are fully visible. The one in his right ear is quite large at this point as it’s grown. it’s taken me months to get in with a surgeon to even evaluate it. I first brought it up to my vet in March and just got my first surgical consult three weeks ago

        1. I think if it is large they may need to do a more invasive surgery. It is so hard to get appointments on a timely basis since the pandemic. I wish you all the best and please keep us posted. If you really wanted, you could get a second opinion.

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