Page 766 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

744 PART IV Specific Malignancies in the Small Animal Patient

TABLE 33.14 Frequency of Clinical Signs Reported
for Dogs with Multiple Myeloma
757,761,762
VetBooks.ir Clinical Sign (n = 112) Frequency Reported (%)

Lethargy and weakness 58
Inappetence and weight loss 36
Lameness 35
Bleeding diathesis 28
Funduscopic/ocular abnor- 32
malities
Polyuria/polydipsia 30 • Fig. 33.28 Necropsy specimen of a spleen from a cat with multiple
myeloma showing diffuse plasma cell infiltration.
CNS deficits 8

CNS, Central nervous system. demonstration of serum or urine myeloma proteins (M compo-

nent) (see Fig. 33.24). In the absence of osteolytic bone lesions,
a diagnosis can also be made if marrow plasmacytosis is associ-
ated with a progressive increase in the M-component or if plasma
TABLE 33.15 Approximate Frequency of Clinical Signs cell clonality (e.g., PARR) is documented. In the cat, because
the degree of bone marrow infiltration may not be as marked, it
Reported for Cats with Myeloma-Related has been suggested that consideration of plasma cell morphology
Disorders (n = 68) 764,767,769–771,788
and visceral organ infiltration (Fig. 33.28) be given in cases with
Clinical Sign Frequency Range Reported (%) demonstrable M-component disease in the absence of marked
(<20%) marrow plasmacytosis. 767,771,786
Lethargy and weakness 40–100
All animals suspected of plasma cell tumors should receive a
Anorexia 33–100 minimal diagnostic evaluation including a CBC, platelet count,
Pallor 30–100 ionized calcium, serum biochemistry profile, and urinalysis. Partic-
ular attention should be paid to renal function and serum calcium
Polyuria/polydipsia 13–40 levels. If clinical hemorrhage is present, a coagulation assessment
Vomiting/diarrhea 10–30 (e.g., platelet count, PT, PTT) and serum viscosity measurements
are indicated. All animals should undergo a careful funduscopic
Dehydration 20–33 examination. Serum electrophoresis and immunoelectropho-
Palpable organomegaly 20–25 resis are performed to determine the presence of a monoclonal
M-component (see Fig. 33.24) and to categorize the immuno-
Lameness 7–25
globulin class involved. Heat precipitation and electrophoresis of
Heart murmur 0–45 urine may be performed to determine presence of Bence Jones
proteinuria because commercial urine dipstick methods are not
Hind limb paresis/paralysis 0–45
capable of this determination. Definitive diagnosis usually fol-
Bleeding diathesis 0–40 lows the performance of a bone marrow aspiration in the dog. A
bone marrow core biopsy or multiple aspirations may be necessary
CNS signs 13–30
because of the possibility of uneven clustering or infiltration of
Concurrent cutaneous 0–30 plasma cells in the bone marrow. Normal marrow contains less
plasma cell tumor than 5% plasma cells, whereas myelomatous marrow often greatly
Fundic/ocular changes 13–33 exceeds this level. Current recommendations require more than
20% marrow plasmacytosis to be present, although a 10% cutoff
Lymphadenopathy 0–10 in cats has been recently recommended with special attention to
cellular atypia. 767 Even the 10% threshold may be problematic in
CNS, Central nervous system.
cats, and cellular atypia and visceral organ involvement (assessed
through needle aspiration cytology or tissue biopsy) should be
considered equally important in this species. 767,771,786 Rarely,
secondary to renal disease or hypercalcemia, and dehydration may biopsy of osteolytic lesions (i.e., Jamshidi core biopsy; see Chap-
develop. Hindlimb paresis secondary to osteolysis and instability ter 25) is necessary for diagnosis in the dog. In one case of MM
of lumbar vertebral bodies or extradural compression has been in a dog, splenic aspirates were diagnostically helpful. 833 Overall
reported in cats. 770,832 frequencies of clinical diagnostic abnormalities for dogs and cats
with MM are compiled from published series having at least five
Diagnosis and Staging cases each and are listed in Table 33.16.

The diagnosis of MM in dogs usually follows the demonstra- Immunohistochemical and Molecular Diagnostics
tion of bone marrow plasmacytosis (see Fig. 33.23), the presence Histochemical and IHC analyses of cells or tissues suspected of
of osteolytic bone lesions (see Figs. 33.25 and 33.26), and the MRD are more often applied in the case of solitary plasmacytomas