Page 1326 - Small Animal Internal Medicine, 6th Edition

1298 PART XII Oncology

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A C

E

B D

FIG 79.6
Leukocyte graphics (dot plots) from four dogs with lymphoma obtained with a ProCyteDx
(Idexx Laboratories, Westbrook, ME). Note the difference in the lymphocyte (blue arrrows)
and monocyte (red arrows) clouds when compared with a normal dog, and the straight
line between both populations. Panels A and B, small and intermediate cell lymphomas;
panels C and D, large cell lymphomas; panel E, normal dog.

in dogs with mediastinal lymphoma than in those with the Polyclonal gammopathies may also be present in cats and
multicentric, alimentary, or extranodal forms. In most dogs dogs with lymphoma. Recently, we identified high serum
with lymphoma and hypercalcemia, the tumor is of T-cell SDMA concentrations in some dogs and cats with lymphoma
origin. or lymphoid leukemia.
Numerous molecular mechanisms underlie hypercalce- Imaging
mia in dogs with lymphoma, but in most cases, hypercalce- Radiographic abnormalities in cats and dogs with lym-
mia is thought to occur as a result of the production of a phoma vary with the different anatomic forms but in general
parathyroid hormone-like protein, called PTHrP (PTH- are secondary to lymphadenopathy or organomegaly (i.e.,
related protein), by the neoplastic cells. Markedly increased hepatomegaly, splenomegaly, renomegaly); occasionally, the
serum concentrations of 1,25-vitamin D have been docu- infiltration of other organs (e.g., lungs) may lead to the
mented in dogs with lymphoma and hypercalcemia by one appearance of additional radiographic abnormalities.
of the authors (GC). Radiographic changes in cats and dogs with multicentric
Hyperproteinemia is another paraneoplastic abnormality lymphoma include sternal or tracheobronchial lymph-
that occurs rarely in cats and dogs with lymphoma. It may adenopathy or both (Fig. 79.7); interstitial, bronchoalveolar,
be secondary to the production of a monoclonal protein by or mixed pulmonary infiltrates; pleural effusion (rare); intra-
the lymphoma cells and can result in the development of abdominal lymphadenopathy (e.g., mesenteric or iliac);
hyperviscosity syndrome. In a recent study of serum protein hepatomegaly; splenomegaly; renomegaly; or intraabdominal
electrophoresis in 155 cats, only one cat had a monoclonal masses. Rarely, lytic or proliferative bone lesions are identi-
gammopathy associated with lymphoma (Taylor et al., 2010). fied on plain abdominal or thoracic radiographs.