Veterinary Society of
Surgical Oncology

General Considerations
  • plasma cell tumors can be single (i.e., solitary or extramedullary plasmacytoma) or diffuse (i.e., multiple myeloma)
  • plasma cell tumors arise from a monoclonal (occasionally biclonal) B-lymphocyte cell lineage
  • solitary masses of monoclonal plasma cell tumors can originate in either soft tissue or bone:
  • soft tissue plasmacytoma = extramedullary plasmacytoma
  • bone plasmacytoma = solitary plasmacytoma
  • cutaneous, oral, and tracheal extramedullary plasmacytomas are benign
  • non-cutaneous extramedullary plasmacytoma have a more aggressive behaviour with gastrointestinal plasmacytoma frequently metastasizing to regional lymph nodes
  • however, rectal plasmacytomas have a good prognosis with low metastatic rate
  • metastatic extramedullary plasmacytomas do not have a monoclonal gammopathy
  • solitary plasmacytoma will often progress to multiple myeloma and may be a precursor to multiple myeloma
  • solitary plasmacytoma have a better prognosis in humans, but 50% will still develop multiple myeloma despite appropriate treatment
  • 5 subclassifications: mature to polymorphous-blastic, but no prognostic significance


  • definitive diagnosis of solitary plasmacytoma requires biopsy proven plasmacytoma in a single site, with:
  • normal bone marrow biopsy
  • normal serum and urine electrophoresis
  • absence of other skeletal lesions
  • normal serum or ionized calcium concentrations
  • absence of anemia
  • normal renal function


General Considerations

  • mean age 9-10 years
  • no sex predilection
  • breed predisposition: German Shepherd Dog
  • sites: trunk, limb, head (especially pinnae), and oral cavity (i.e., tongue and gingiva)


  • pleomorphic round cells with immunoreactivity to canine IgG and vimentin
  • systemic involvement rare with only 1 case reported with hypercalcemia and hypergammaglobulinemia


  • surgery or radiation therapy
  • surgery, radiation therapy, or chemotherapy (i.e., melphalan and prednisone) for recurrent tumors


  • prognosis is excellent with:
  • 1.2% develop systemic multiple myeloma
  • 3.8% local tumor recurrence rate with majority of recurrences due to incomplete resection
  • 1.8% develop metastasis to other cutaneous sites


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