Page 1327 - Small Animal Internal Medicine, 6th Edition

CHAPTER 79 Lymphoma 1299

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FIG 79.7 FIG 79.8
Mediastinal, hilar, and sternal lymphadenopathy in a dog Mesenteric lymphadenopathy in a 12-year-old cat with
with multicentric lymphoma. diarrhea associated with an intestinal small cell lymphoma.
Note the marked enlargement of the affected lymph node
(3 × 5 cm).

In cats and dogs with mediastinal lymphoma, radio- 2010). Fine-needle aspiration (FNA) and needle biopsy
graphic changes are usually limited to the finding of an ante- can also be easily performed using this technique to guide
rior (or, more rarely, posterior) mediastinal mass, with or the placement of the needle. Ultrasonography is neither
without pleural effusion. In cats and dogs with alimentary sensitive nor specific for the evaluation of liver lesions; a
lymphoma, abnormalities are rarely detected on plain high proportion of dogs with hepatic lymphoma have nor-
abdominal radiographs (<50%). When present, they vary in mal ultrasonographic appearance. Therefore obtaining a
nature but include mainly hepatomegaly, splenomegaly, and sample for cytology in patients with ultrasonographically
midabdominal masses. Positive contrast–enhanced radiog- normal liver is recommended in dogs with lymphoma or
raphy of the upper gastrointestinal tract usually reveals suspected lymphoma.
abnormalities in most animals. In a series of dogs with ali-
mentary lymphoma evaluated at one authors’ clinic (GC), Diagnosis
abnormalities were found in all dogs that underwent positive The clinical signs and physical examination findings
contrast–enhanced radiography of the upper gastrointestinal described in preceding paragraphs are usually suggestive of
tract and included mucosal irregularities, luminal filling lymphoma. However, before instituting therapy, the clinician
defects, and irregular thickening of the wall, suggestive of must confirm the diagnosis cytologically, histopathologi-
infiltrative mural disease. cally, or, less frequently, using molecular techniques. In addi-
Ultrasonography constitutes an invaluable tool for tion, a minimum database consisting of a CBC, serum
evaluating cats or dogs with suspected or confirmed intra- biochemistry profile, and urinalysis should be obtained if the
abdominal lymphoma. The technique is also helpful in the owners are contemplating treatment.
evaluation of mediastinal masses in both species (see Chap- From a cytologic standpoint, lymphomas can be classi-
ter 78). Changes in the echogenicity of parenchymal organs fied as small-, intermediate-, or large-cell types. As a general
(i.e., liver, spleen, kidneys) detected by this technique usu- rule, small-cell lymphomas are slowly progressive (i.e., indo-
ally reflect changes in organ texture secondary to neoplastic lent), whereas large-cell lymphomas are more aggressive.
infiltration. In addition, enlarged lymphoid structures or Intermediate-cell lymphomas can be indolent or aggressive.
organs can easily be identified using this technique. Several In most dogs and cats with large-cell multicentric, superficial
abnormalities are commonly detected ultrasonographically extranodal, mediastinal, or alimentary lymphoma, a diag-
in cats and dogs with intraabdominal lymphoma, including nosis can easily be obtained by cytologic evaluation of FNA
hepatomegaly; splenomegaly; changes in the echogenicity of of the affected organs or lymph nodes. The techniques for
liver or spleen (mixed echogenicity or multiple hypoechoic FNA and the cytologic features of lymphoma are described
areas); diffuse, focal, or multifocal intestinal thickening; in detail in Chapter 74 (Fig. 79.9).
lymphadenopathy (Fig. 79.8); splenic masses; and effusion. In the authors’ practices, lymphomas can be diagnosed
Cats with lymphoma of the small intestine are more likely cytologically in over 90% of dogs and 70% to 75% of cats
to have thickening of the muscularis when compared with evaluated. In other words, in only 10% of the dogs and 25%
cats with inflammatory bowel disease (Zwingenberger et al., to 30% of the cats is it necessary to perform a histopathologic,