Page 411 - Problem-Based Feline Medicine

20 – THE CAT WITH ENLARGED LYMPH NODES 403

NODAL LYMPHOMA* Clinical signs
Solitary, regional (especially mandibular or cervical)
Classical signs or generalized, moderate to marked painless periph-
eral lymphadenopathy.
● Painless lymphadenopathy.
● Non-Hodgkin’s lymphoma may occur at any age.
The average age for cats with multicentric lym-
phoma is 4 years.
Pathogenesis ● Most cats with Hodgkin’s-like lymphoma are > 6
years of age (range 1–14 years).
Based on the histological classification in humans,
Cats may not have other historical signs, or may have
lymphoma in cats may be classified as non-Hodgkin’s
lethargy, inappetence and weight loss.
lymphoma and Hodgkin’s-like lymphoma. The latter
has been recently recognized. Hepatosplenomegaly may be present.
● Non-Hodgkin’s lymphoma includes the most
Mediastinal lymphoma and alimentary lymphoma are
commonly recognized forms of lymphoma in cats,
not typically associated with peripheral lymphadenopa-
including mediastinal, alimentary, multicentric,
thy, although nodal involvement occasionally occurs.
other extra-nodal lymphomas and lymphocytic
leukemia.
● Primary multicentric nodal lymphoma (initial site Diagnosis
of disease is a lymph node) causes generalized
Diagnosis requires finding lymph node cytology con-
peripheral lymphadenopathy from malignant lym-
sistent with lymphoma, and biopsy-confirmed
phoid cell proliferation.
lymphoma (cytology or histology) at another site, e.g.
● The disease may metastasize to the bone marrow
bone marrow, liver, spleen.
(leukemic lymphoma) and liver and spleen.
● Primary lymphocytic leukemia (initial site of dis- If lymphoma cannot be confirmed at another site, exci-
ease is the bone marrow) may metastasize to sional lymph node biopsy and histology are manda-
peripheral nodes and cause lymphadenopathy. tory to distinguish from atypical hyperplasia and to
● Non-Hodgkin’s nodal lymphoma less commonly characterize the lymphoma.
involves solitary or regional nodes, and occasion-
FeLV and FIV tests should be obtained.
ally solitary to generalized nodal involvement
accompanies other forms (e.g. mediastinal lym-
phoma). Differential diagnosis
● Historically, multicentric nodal lymphoma and
Differential diagnoses for generalized lymph-
lymphocytic leukemia in most cats has been associ-
adenopathy include atypical hyperplasia, hyperplasia
ated with FeLV infection. However, as the preva-
in response to generalized skin diseases, immunologic
lence of FeLV declines in some regions, the
disorders and systemic infections, widely metastatic
incidence of FeLV-negative nodal lymphoma is
neoplasia, and generalized bacterial or fungal lym-
increasing.
phadenitis.
● FIV infection increases the risk of non-Hodgkin’s
lymphoma. Differential diagnoses for solitary or regional lymph-
adenopathy include plexiform vascularization of
Hogkin’s-like lymphoma histologically resembles
lymph nodes, atypical hyperplasia, hyperplasia in
“lymphocyte-predominance Hodgkin’s disease” in
response to local tumors, oral cavity and skin diseases,
humans.
and infections, metastatic lymphadenopathy, and bacte-
● Most cases involve a solitary mandibular or cer-
rial or fungal lymphadenitis.
vical node. Solitary inguinal, regional cervical and
generalized lymphadenopathy have also been rec- These are distinguished on the basis of lymph node
ognized. cytology, histology and culture and work-up for an
● Most cats tested are FeLV and FIV negative. underlying disease.