Page 421 - Problem-Based Feline Medicine

20 – THE CAT WITH ENLARGED LYMPH NODES 413

Diagnosis sound examinations, bone marrow biopsy, lymph
node bacterial/fungal culture, biopsies of other
Lymph node cytology consistent with hyperplasia,
abnormal organs (submit for cytology/histology
lymphoma, or suspicious for lymphoma.
and culture), tests for Bartonella henselae and
Lymph node histology reveals marked hyperplasia with Ehrlichia sp. infection (see page 417), serologic
disruption of lymph node architecture. tests for fungal agents, and antinuclear antibody
● Characteristic findings in the first case series were and lupus erythematosus cell tests.
paracortical hyperplasia with histiocytes, lympho- – Although FIP may cause mesenteric lymph-
cytes, plasma cells, and immunoblasts, and post- adenopathy, peripheral lymphadenopathy has not
capillary venular proliferation. been reported.
● Characteristic findings in the second case series
were paracortical, follicular or diffuse lymphoid
expansion, but other findings typical of lymphoid Differential diagnosis
malignancy were variably absent.
Lymphadenopathy is a problem and not a diagnosis,
Idiopathic lymphadenopathy is not a diagnosis in and as such this discussion of idiopathic generalized
itself. Lymph node hyperplasia is an immune reaction lymphadenopathy is an extension of the Introduction.
to a cause. Atypical hyperplasia represents either an
The most common causes of generalized lymph-
unusual cause or an atypical response to a usual cause.
adenopathy are generalized skin diseases, FeLV/FIV
Aggressive diagnostic evaluation should be performed
infections and lymphoma.
to reveal infection or neoplasia, especially since multi-
● Skin lesions are usually obvious if lymphadenopa-
system immune-mediated diseases such as systemic
thy is due to a skin disease.
lupus erythematosus are rare in cats. Work-up
● If a cat is FeLV- and/or FIV-positive, the possibility
includes:
of concurrent neoplasia or infection contributing to
● FeLV test.
lymphadenopathy should be considered.
● If an ELISA (enzyme-linked immunosorbent assay)
● Nodal lymphoma is one of the less common
test on blood is negative, and another cause of lymph-
forms of lymphoma.
adenopathy has not been found, obtain a FA (fluo-
– It may be solitary, regional or generalized, simi-
rescent antibody) or PCR (polymerase chain
lar to cats with atypical hyperplasia.
reaction) test on blood. If negative, obtain a FA or
– Cats may have no historical signs other than
PCR test on a bone marrow or lymph node aspirate,
lymphadenopathy, similar to cats with atypical
or immunohistochemistry test on a bone marrow
hyperplasia.
core or lymph node biopsy. It should be noted that
– Excisional biopsy is mandatory and communi-
PCR testing has not been standardized and is more
cation with the pathologist essential to rule in or
likely to give false-positive results than ELISA and
rule out lymphoma.
FA if the laboratory does not maintain the highest
– There may be evidence of lymphoma at another
standards of quality control.
site, e.g. bone marrow, liver, spleen or the dis-
● FIV test.
ease will progress to involve these sites.
● Search for other infections and neoplasia.
Hepatosplenomegaly was not reported in the
– Detailed review of history of physical examina-
case series where lymph node histology resem-
tion for subtle signs, including ophthalmologic
bled lymphoma.
examination.
– Further work-up will depend on clinical signs,
exposure risks for infectious agents and financial Treatment
considerations.
Treatment should be supportive if needed pending a
– Diagnostic evaluation may include complete
diagnosis.
blood count, serum chemistry profile, urinalysis,
blood culture, urine culture, abdominal and tho- If the owner refuses a work-up, and the cat is otherwise
racic radiographs, cardiac and abdominal ultra- normal, encourage observation rather than euthanasia.