Plasmacytoma In Dogs

Plasmacytoma is an uncommon tumor of dogs. There are two forms, medullary and extramedullary according to whether the growth is in the bone marrow or not, respectively. Today we will be discussing extramedullary plasmacytoma. This is a continuation of our series on round cell tumors which began with canine histiocytoma, followed by canine transmissible venereal tumor.

Canine extramedullary plasmacytomas are most likely to occur on mucus membranes and/or skin. The head is a common location for them, with the areas of the face, ears and lips frequently affected. However, lesions also commonly occur on the trunk as well as the feet and toes.

Typically canine extramedullary plasmacytoma is a tumor of older dogs. They arise with the appearance of raised, red nodules. Rarely is the general health of the patient affected unless the mass is in the mouth or rectum, in which case obstruction may occur.

Differential diagnosis must include multiple myeloma, especially if systemic disability is observed.

Treatment is primarily focused on surgical excision. However, given the typical locations in which they occur, surgical excision may, by necessity, be incomplete. For example, rectal and oral lesions may not allow removal of all of a tumor mass if large quantities of tissue must be excised. Sufficient skin to close a surgical site may exist for a small foot lesion, but this is a part of the body which has little skin to spare. Large lesions may require amputation.

On the other hand, growths on the trunk usually allow for wide surgical margins, removing all of the cancerous cells. In these cases prognosis is favorable.

For plasmacytomas which cannot be completely removed surgically, chemotherapy and radiation are good treatment options for many patients.

See you tomorrow, Dr. Randolph.


  1. Hi Everyone! I am so confused about plasmacytoma. I found a red bump on my Yorkie on the side of his belly, at the bottom of his right rib cage. I thought it would go away, but after comparing it to some pictures on the internet, I took him to the vet. They did a biopsy and it came back benign plasmacytoma. They suggested surgery, but my confusion comes from what the vet said and what I’ve read, which is that it is highly unlikely to turn into cancer or spread. That being said, I am wondering why the need to remove it. I hate to risk putting him under if I don’t have to, but am wondering if I am putting him at risk in some way if I just leave it.

    Please can someone clarify this for me.

    • There are two prime advantages to surgical removal. One, it gets the mass off while it’s still small. Even benign growths can get to be huge. Second, if the initial diagnosis was obtained by fine needle aspirate, a pathologist’s evaluation of the actual tissue can be more accurate in some cases. Thanks for reading, Dr. Randolph.

  2. My miniature Dachshund I recently acquired from a Dachshund rescue had to have multiple surgeries in a relatively short time period. The problem I am writing about is a plasmacytoma aboutvthe size of a marble beside her right inner toe pad. It makes it difficult for her to walk. One vet recommends just tunneling around it to remove the mass. The other on recommends removing the toe. Both say these types of growths recur. She is nine years old and I have only had her two weeks. She has only two canines left in her mouth, the rest were removed Jan. 17. She must be on C/D formula food for struvite stones. She had seven of those removed the size of nickels on Jan. 25. I got her Feb. 9. One would be hard pressed to find a sweeter dog. I would appreciate your recommendations. Thank you for them and this site!

  3. My almost 10 year old golden retriever had to have a lump removed from her leg and during this time we also had a red lump in her ear checked with a FNA. The lump in her ear is right in the centre on the cartilage of the inside of her ear and is the size of a pencil eraser and very red. The vet tried squishing it (not sure why) maybe trying to figure out what it was ??!! Anyway we did do a FNA to determine what it was when she had surgery for the lump on her leg to be removed.

    I would love to know your thoughts on the report below – this was just taken last week. My vet advised me to leave the lump and to just observe it for changes. Because of its location it is in the ear it requires a more difficult removal. Again the vet advised to just leave the lump and observe changes in the lump closely.

    Thoughts ? Welcome your thoughts ? Thank you kindly.

    We found out it is plasma cytona – the report said – two small smears from an aspirate of a red round smooth dermal mass attached to the cartilage in the ear are evaluated. The smears are mildly to moderately cellular and hemodiluted with a few small platelets clumps. The background is clear to lightly pale and eosinophilic and contains scattered bare/smudged nuclei and a few small streams of nuclear material admixed amongst variable numbers of erythrocytes . The nucleated cells consist of a round cell population. These cells have variable amounts of deeply basophilic cytoplasm and a single round to ovoid nucleus that is the centrically located and has a stippled to slightly clumped chromatin pattern and indistinct nucleoli. Some cells have a characteristic perinuclear clear golgi zone. Occasional binucleate cells are noted. Anispcytosis and anisokaryosis is mild to moderate within this population. Mitotic figure aren’t identified. A single Mott cell is noted. The remaining nucleated cells consist consist of scattered inflammatory leukocytes, that do not appear to be increased in relation with the degree of hemorrhage noted. Etiologic agents are not identified. Interpretation : plasma cytoma.
    The cytologic findings are consistent with a cutaneous plasma cytoma , cutaneous plasma cytoma are typically benign tumours seen in middle age to older dogs.

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