Page 1316 - Cote clinical veterinary advisor dogs and cats 4th

664 Multiple Myeloma and Plasma Cell Tumors

• Focal/diffuse bone lesions: due to proliferating Advanced or Confirmatory Testing • IV fluids (if HVS) for hydration and diuresis
malignant plasma cells (causing pathologic MM: to decrease serum viscosity, azotemia, and
VetBooks.ir • M protein in blood increases serum viscos- must be met: monoclonal gammopathy, • Analgesia for bone pain
• In dogs, two of the following four criteria
hypercalcemia
fractures in dogs but rarely in cats)
lytic bone lesions, plasma cell infiltration
ity, causing hyperviscosity syndrome (HVS
○ Bisphosphonate drugs (e.g., pamidronate
[p. 509]).
• The light chain portion of the Ig, also called of the bone marrow, and Bence Jones 1-2 mg/kg diluted to 250 mL in sterile
0.9% NaCl and given as 2-hour IV
proteinuria.
the Bence Jones protein, is small enough to ○ Serum protein electrophoresis (p. 1375): infusion) are an option to reduce bone
be filtered by the normal glomerulus. They monoclonal gammopathy pain and may lower the risk of patho-
can be detected in the urine of patients with ○ Survey radiographs: in dogs, multiple areas logic fracture in patients with lytic bone
MM with the Bence Jones screening test or of bony lysis or diffuse osteopenias are disease or osteopenia. Oral forms are not
quantitative protein test (but not on a urine common (vertebrae, scapulae, long bones) recommended (poor bioavailability in
dipstick) (p. 1311). and/or pathologic fractures; not typically animals).
• Kidney disease develops secondary to Bence found in cats. A solitary area of lysis is Radiation therapy can be palliative for SOP or
Jones proteinuria, tumor infiltration into typical of SOPs. a localized painful lytic bony lesion.
kidney, hypercalcemia, amyloidosis, and/or ○ Bone marrow aspiration: > 10% plasma • Plasmapheresis to remove Bence Jones
decreased renal perfusion. cells with atypia or > 20% plasmacytosis is proteins (decrease serum viscosity) may be
• Hypercalcemia occurs from release of required for the diagnosis of MM. Aspira- available at some institutions. Therapeutic
osteoclast-activating factor by neoplastic tion of multiple sites may be necessary. phlebotomy (with donor red blood cell
cells. Marrow infiltration is uncommon in cats. transfusion) can possibly achieve a similar
• Cytopenias develop from bone marrow ○ Heat precipitation or electrophoresis of effect.
infiltration and blood loss due to bleeding urine (Bence Jones test): identifies Bence • Prophylactic, broad-spectrum antibiotic
tendencies (from protein coating of platelets Jones proteins, which are not detected on therapy to treat infections (urinary, pneumo-
and inhibition of platelet and coagulation urine dipstick. nia), avoiding nephrotoxic or bacteriostatic
factor release). • Abdominal ultrasound (especially in cats): to antibiotics
• An increased susceptibility to infection is identify possible sites of organ involvement.
seen because of the suppression of normal In cats, abdominal organ infiltration (e.g., Chronic Treatment
Ig levels, leukopenias, and impaired cell- liver, spleen) by neoplastic plasma cells is • Chemotherapy: melphalan and prednisone
mediated immunity. Urinary tract infections more common, and ultrasound-guided are the mainstay of treatment for MM
and pneumonia are common manifestations. fine-needle aspiration for cytology should in dogs and cats. Cyclophosphamide can
be considered, especially if organomegaly is alternatively be given initially in cases of
DIAGNOSIS present and there are no contraindications widespread disease or severe hypercalcemia
(e.g., bleeding tendency). because this regimen is thought to have a
Diagnostic Overview ○ If necessary, additional confirmatory more rapid clinical effect, but the benefit is
• MM typically is first considered when diagnostics can be performed on cytology unclear in dogs. Melphalan causes erratic
hyperglobulinemia is found on a serum bio- slides, including special stains to determine myelosuppression in cats; substituting
chemistry profile, osteolytic lesions are seen whether the cells noted are plasma cells chlorambucil or cyclophosphamide has been
radiographically, or an unexplained bleeding and/or clonality testing to prove that a advocated. Response rates and survival times
disorder occurs. Diagnosis requires any two population of plasma cells is monoclo- with cyclophosphamide plus prednisolone
or more of these findings: monoclonal gam- nal (neoplastic) rather than polyclonal are similar to melphalan plus prednisolone
mopathy on serum protein electrophoresis, (inflammatory): immunocytochemistry for for cats. Chemotherapy can be attempted in
lytic bone lesions on radiographs, Bence MUM-1, and polymerase chain reaction cases of cutaneous PCT, EMP, or SOP that
Jones proteinuria on specific urine assay, and/ (PCR) for antigen receptor rearrangement are nonresectable or if radiation therapy is
or plasma cell infiltration of bone marrow (PARR), respectively. not available. However, response information
on bone marrow aspirate/biopsy. • Serum or urine immunoelectrophoresis: is limited. Other cytotoxic drugs (doxoru-
• PCTs usually present as discrete masses identifies the Ig class (IgG, IgM, IgA) bicin, vincristine, CCNU [lomustine], and
(typically cutaneous); aspiration is often • Serum viscosity may be measured in some Tanovea [rabacfosadine]) may have some
confirmatory because of the distinctive labs to verify HVS. activity in the rescue setting for some patients
appearance of plasma cells. PCT: with MM. Consultation with an oncologist
• Tissue biopsy confirmation of cutaneous for the most current treatment options is
Differential Diagnosis PCT, EMP, and SOP recommended.
Differentials for monoclonal gammopathy: • Immunohistochemistry for the marker • Radiation therapy is the treatment of choice
ehrlichiosis, leishmaniasis, feline infectious MUM-1 can help differentiate lymphoma for SOP, some incompletely excised PCTs,
peritonitis, pyoderma, lymphoma, leukemia, from PCTs if needed. and localized MM bony lesions.
idiopathic (monoclonal gammopathy of • Surgical excision is curative for most cutane-
unknown significance) TREATMENT ous PCTs.
Initial Database Treatment Overview Recommended Monitoring
• Funduscopic exam: hemorrhage, retinal Goals of treatment are to reduce myeloma cell • Monitor CBCs frequently (myelosuppressive
detachment, dilated/tortuous vessels may burden, relieve bone pain, allow skeletal healing, effects of melphalan), and alter dosage or
occur due to hyperviscosity and decrease serum viscosity and Ig levels. schedule based on patient response.
• CBC: cytopenias, thrombocytopenia, increased • Monitor serum electrophoresis because size
total protein Acute General Treatment of monoclonal spike is proportional to tumor
• Serum biochemistry panel: hypercalcemia, • Stabilize fractures. burden. Plasma globulin level can also be
elevated total protein, hyperglobulinemia, • Surgical excision of PCTs if possible; wide used for monitoring remission status.
azotemia possible surgical margins generally are not necessary, • Monitor for evidence of infection, and
• Urinalysis: infection possible (immunosup- but margins should be free of gross and treat with antibiotics as needed due to
pression), isosthenuria if in renal failure microscopic evidence of neoplasia. immunosuppression.

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