Plasma cell tumors

Question 1

What are plasma cell tumors

Answer 1

Plasma cell tumors are tumors of the plasma cell lineage of B-lymphocytes

These are rare in cats and are usually not associated with FeLV or FIV infection

Question 2

What is plasmacytoma

Answer 2

Plasmacytoma is a solitary plasma cell tumor that tends to be in an extra-medullary location
- occasional solitary plasmocytomas of bone have been reported

Question 3

What are multiple myelomas

Answer 3

Multiple myelomas are plasma cell tumors that affect the bone marrow at more than one site or the bone marrow plus systemic involvement

The neoplastic cells over-secrete immunoglobulin and/or a component of immunoglobulin (e.g., heavy or light chain) which typically results in a monoclonal hyperglobulinemia
- in around 25% or less, there may be a bi-clonal spike on protein electrophoresis

Question 4

What are the consequences of the over-secretion of immunoglobulin in multiple myeloma

Answer 4

The paraproteinemia may result in:
- hyperviscosity syndrome and secondary neurological signs
- in up to 50% of cases there may be Bence-Jones proteinuria

Question 5

How is a diagnosis of multiple myeloma made

Answer 5

The diagnosis is typically made hen two or more of the following are present:
- paraproteinemia/monoclonal gammopathy
- Bence-Jones proteinuria
- radiographic evidence of osteolytic bone lesions (only 50% of cases)
- > 5% neoplastic plasma cells in the bone marrow (or > 20% plasma cells in the blood)

The presence of extra-medullary masses (e.g., liver, lymph nodes, spleen) containing neoplastic plasma cells may also be helpful diagnostically

Question 6

What is the prognosis and treatment for multiple myeloma

Answer 6

The prognosis is guarded but some cats appear to respond well

Therapy is usually with a combination of prednisolone and melphalan
- prednisolone 0.5 mg/kg, q24h for 10 days then 0.5 mg/kg, EOD
- melphalan 2 mg/m2 EOD