Page 1323 - Small Animal Internal Medicine, 6th Edition

CHAPTER 79 Lymphoma 1295

TABLE 79.1 regurgitation (the latter is more common in cats) of recent
onset. Polyuria and polydipsia are also common presenting
VetBooks.ir Prevalence of Feline Leukemia Virus Infection in Cats complaints in dogs with mediastinal lymphoma and hyper-
calcemia; tumor-associated hypercalcemia is rare in cats
With Lymphoma
ANATOMIC FORM FeLV POSITIVE (%) with lymphoma. The respiratory and upper digestive tract
signs are caused by compression from enlarged anterior
mediastinal lymph nodes, although malignant pleural effu-
Alimentary 30 sion can contribute to the severity of the respiratory tract
Mediastinal 90 signs. On physical examination, the abnormalities are usually
Multicentric 80 confined to the thoracic cavity and consist of decreased
Cutaneous 0 bronchovesicular sounds, normal pulmonary sounds dis-
placed to the dorsocaudal thoracic cavity, a dull sound heard
on percussion of the ventral thoracic cavity, and a noncom-
pressible anterior mediastinum (in cats). Unilateral or bilat-
eral Horner syndrome may occur in cats (and occasionally
dogs) with mediastinal lymphoma. Some dogs with medias-
tinal lymphoma have marked head and neck edema caused
by compression from enlarged lymph nodes (anterior vena
cava syndrome).
Cats and dogs with alimentary lymphoma usually display
gastrointestinal tract signs such as anorexia, vomiting, diar-
rhea, or weight loss. Occasionally, signs compatible with an
intestinal obstruction or peritonitis (caused by rupture of a
lymphomatous mass) can occur. Physical examination typi-
cally reveals an intraabdominal mass or masses (e.g., enlarged
mesenteric or ileocecocolic lymph nodes or intestinal
masses) and thickened bowel loops (in patients with diffuse
small intestinal lymphoma). Rarely, polypoid lymphomatoid
masses can protrude through the anus in dogs with colorec-
tal lymphoma.
FIG 79.1 The clinical signs and physical examination findings in
Massive mandibular lymphadenopathy in a dog with
multicentric lymphoma. (Courtesy Dr. Bill Kisseberth.) cats and dogs with extranodal lymphomas are extremely vari-
able and depend on the location of the lesions. In general, the
clinical signs stem from the compression or displacement of
the multicentric form are evaluated because of vague, non- normal parenchymal cells in the affected organ (e.g., anterior
specific clinical signs, or more frequently, the owners detect uveitis or hyphema in ocular lymphoma, variable neuro-
one or more subcutaneous masses (i.e., enlarged lymph logic signs in central nervous system [CNS] lymphoma). The
nodes, Fig. 79.1) during grooming or petting in an otherwise typical clinical signs and physical examination findings in
healthy pet, and this prompts them to seek veterinary care. cats and dogs with extranodal lymphomas are summarized
Occasionally, dogs and cats with lymphoma are evaluated in Table 79.2. Common extranodal forms in dogs include
because of nonspecific clinical signs such as weight loss, cutaneous and ocular lymphomas; in cats they include naso-
anorexia, and lethargy. If the enlarged lymph nodes mechan- pharyngeal, ocular, renal, and neural lymphomas.
ically obstruct lymphatic drainage, edema can occur; if they Cutaneous lymphoma is one of the most common extra-
compress the airway, coughing may occur. Dogs with lym- nodal forms of lymphoma in dogs but is rare in cats. The
phoma and hypercalcemia (see later) frequently present for clinical signs and characteristics of the lesions are extremely
polyuria and polydipsia, and are often times clinically unwell. variable, and they can mimic any primary or secondary skin
Physical examination of dogs and cats with multicentric lesion. Dogs with mycosis fungoides (an epitheliotropic
lymphoma usually reveals marked to massive generalized T-cell lymphoma) are usually first evaluated because of
lymphadenopathy, with or without hepatomegaly, spleno- chronic alopecia, desquamation, pruritus, and erythema,
megaly, or extranodal lesions (e.g., ocular, cutaneous, renal, eventually leading to plaque and mass formation (Fig. 79.2).
neural). The affected lymph nodes are enlarged, painless, Mucocutaneous and mucosal lesions are relatively common,
and freely movable. A syndrome of reactive (hyperplastic) but generalized lymph node involvement may not occur ini-
lymphadenopathy that occurs in cats can mimic the clinico- tially. A characteristic lesion in dogs with this form of lym-
pathologic features of multicentric lymphoma but is usually phoma is a circular, raised, erythematous, donut-shaped,
easily distinguished cytologically. dermoepidermal mass that contains normal skin in the
Cats and dogs with mediastinal lymphoma are usually center (Fig. 79.3). Diffuse swelling and erythema are also
evaluated because of dyspnea, coughing, or dysphagia/ common (Fig. 79.4, A). Most of the cats with cutaneous