Page 751 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 33 Hematopoietic Tumors 729

histologic characterization of uveitis in cats, lymphoma was diag-
nosed in approximately one-third of cases; however, whether these
were part of a systemic process or limited to the eye was unclear.
596
VetBooks.ir Nearly half of these cases were documented before 1988 and
because nearly half were FeLV antigenemic cats, these data likely
have little bearing on modern incidence of the disease.
Presumed solitary ocular lymphoma (PSOL) is rare in cats and
was identified in 5 of 110 cases of extranodal lymphoma in one
R
report. 559 Cats with ocular lymphoma are presented with uveitis
or iridial masses, as well as signs related to systemic involvement
A of disease.
Only sporadic reports appear in the literature with the major-
ity (approximately 75%) being B-cell immunophenotyped. One
case of LGL PSOL is documented. 559 Intraocular, retinal, and
conjunctival locations are reported. 597–600 Outcomes are poorly
defined in reports; those cases that underwent enucleation often
experienced long-term outcomes with STs of 6 months to 4 years
reported.
B
General Summary of Prognosis for Cats with
• Fig. 33.19 (A) Lateral radiographic projection of a cat with tracheal lym- Lymphoma
phoma before treatment. (B) The same cat 6 weeks after initiation of
CHOP-based chemotherapy protocol. As previously discussed, the prediction of outcome in cats with
lymphoma is not generalizable because of the wide spectrum of
histologic and anatomic subtypes encountered. Much has been
chemotherapy protocols, although many responded or stabilized, mentioned in the previous treatment sections, and Tables 33.9 and
durability was poor and MSTs were approximately 6 months. 592 33.10 summarize prognostic parameters for lymphoma in cats.
Seven cases of tarsal SC-L received chemotherapy and RT with
an MST of 216 days. Because the disease has a high recurrence
and metastatic behavior, it is likely that a multimodality approach Feline Leukemias, Myeloproliferative
involving local therapy (surgery and/or RT) and systemic chemo- Disorders, and Myelodysplasia
therapy would intuitively provide the best outcomes.
For a complete discussion of leukemias and MPDs, including a
Laryngeal/Pharyngeal/Tracheal Lymphoma general discussion of hematopoiesis, etiologies, lineage classifica-
tion and descriptions, see Section C of this chapter. The classi-
Laryngeal lymphoma comprised 10% of 110 cases of extranodal fication of leukemias in cats is difficult because of the similarity
forms in one report and represented 11% of all laryngeal disease in of clinical and pathologic features and the transition, overlap, or
the species. 559,572,594 It occurs in older cats (median age, 9 years), mixture of cell types involved. 601–605 Most cases are from the FeLV
is not associated with FeLV, and may be a solitary lesion or occur era and generally only single case reports exist from the more con-
in the presence of other multicentric sites. No information on temporary post-FeLV era, which further confuses our understand-
immunophenotype is currently available. Signs associated with ing of their biology and outcome. For this reason, only a simplistic
this location in affected cats include dyspnea, dysphonia, stridor, discussion, primarily relating to the lymphoid leukemias will be
gagging or retching, and rarely, coughing. 559,594 Although it is gen- presented here and the interested reader is again referred to Sec-
erally localized to the primary site (stage I), approximately 25% tion C of this chapter for a general discussion of nonlymphoid
had regional nodal involvement in one report. The vast major- leukemia.
ity of cats with laryngeal or tracheal lymphoma respond to either For cats with suspected leukemia, peripheral blood assess-
RT (if localized) or systemic chemotherapy (90% CR to COP- or ment (e.g., CBC with differential, flow cytometric analysis for
CHOP-based protocols) (Fig. 33.19). 528,559 Whereas the author’s size and immunophenotype, and PARR [for lymphoid leuke-
experience is that most have durable responses and STs typically mias]), and bone marrow aspiration or biopsy may contribute to
approach or exceed 1 year, published reported MSTs range from a diagnosis. Cats with acute leukemia are likely to have malig-
5.5 to 9.0 months after achievement of a CR. 561 nant cellular infiltrates in organs other than bone marrow. 603
A bone marrow aspirate with greater than 30% abnormal blast
Ocular Lymphoma cells is sufficient to make a diagnosis of an acute leukemia. In
cats with suspected CLL, infiltration of the bone marrow with
In a compilation of 75 cases of intraocular tumors of cats, 15 more than 15% mature lymphocytes helps support the diag-
(20%) were lymphoma (seven B-cell, four T-cell and four not nosis. 606 All cats with leukemia should be tested for FeLV/FIV.
evaluated). 506 It was presumed, but not proved, that the major- Determining the lineage of some leukemias can be challenging;
ity of these were part of a systemic multicentric process. Indeed, most can be distinguished by histologic appearance, histochemi-
lymphoma was the most common metastatic cancer in the feline cal stains, or immunohistochemical or flow cytometric analysis
eye. In 26 cats surveyed with systemic lymphoma, nearly half of the leukemic cells for cellular antigens that identify their lin-
had some ocular changes with uveitis being most common, fol- eage (see Chapter 8 and Section C of this chapter). 601,605,607 In
lowed by exophthalmos, corneal ulceration, and chemosis. 595 In a addition, examination of blast cells by electron microscopy may