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establish a definitive diagnosis. A histologic evaluation The fluid lymphocyte count is usually greater than
VetBooks.ir of the diseased tissue will provide a more accurate evalu­ 4000/μL, with most appearing as intermediate or large
lymphoblasts. In cases where fluid cytology is not
ation of tissue morphology and degree of invasion. If an
equivocal diagnosis is present, techniques such as immu­
completed via ultrasound or computed tomography
nohistochemical or immunocytochemical analysis, flow diagnostic, aspiration or biopsy of the mass itself can be
cytometric analysis and polymerase chain reaction‐ (CT) guidance. Immunophenotypic and clonality assess­
based clonality assays are available to characterize the ment may be helpful in equivocal cases.
disease and refine the diagnosis.
Currently, a histologic classification scheme similar to Nasal Lymphoma
those described in humans and dogs does not exist for Nasal lymphoma differs from other sites in that it is often
feline lymphoma. There are two histologic forms: high‐ non‐systemic and confined to the nose and/or sinuses.
(or intermediate) grade lymphoma and low‐grade Nasal CT or magnetic resonance imaging (MRI), rhinos­
(or small cell) lymphoma. These histologic distinctions copy, and biopsy are necessary to establish a diagnosis.
in combination with anatomic location are the most Thorough staging with evaluation of regional lymph
prognostic and will determine treatment. nodes, thorax, and abdomen is recommended if local
radiation therapy is to be considered for sole treatment.
Immunophenotype
Immunophenotyping is not commonly used for prog­ Renal Lymphoma
nostication purposes in the cat as it is in dogs and Renal lymphoma usually causes bilateral renomegaly
humans. It is employed, however, to confirm the presence which may be detected on physical exam. Clinical signs
of a phenotypically identical population of lymphoid at presentation are a consequence of renal insufficiency.
cells that make up the tumor. This can be completed Ultrasound‐guided renal biopsy or FNA is recommended
on tissue samples via histochemical or cytochemical to confirm the diagnosis.
staining for CD3 (T cell expression) or CD79a (B cell
expression). According to some studies, a T cell pheno­ Central Nervous System Lymphoma
type is more prevalent in cats with small cell or low‐grade Spinal CNS lymphoma usually causes hindlimb paresis
alimentary lymphoma and B cell phenotype is more or paralysis with or without back pain. Most tumors are
common in large cell or high‐grade lymphoma. As extradural, and occur in the thoracolumbar or lumbosa­
mentioned previously, cell morphology (large cell vs cral regions. Often there is no radiographic evidence of
small cell) is used more commonly than a phenotypic disease. The clinical signs of brain lymphoma are attrib­
distinction to determine treatment and prognosis. utable to the region of brain affected. Advanced imaging
with MRI or CT can be helpful in determining extent
Alimentary Lymphoma and location of the lesion, and to evaluate for multifocal
Cats with alimentary lymphoma are typically diagnosed disease. Because cerebral spinal fluid evaluation is not
via abdominal imaging (e.g., ultrasound), which is abnor­ always definitive for lymphoma, a diagnosis may be
mal in approximately 60–90% of cats. The appearance is attempted through cytologic evaluation of the bone
variable, and may be of a circumferential mass with loss marrow or kidneys since these organs are also involved
of GI wall layering, or of a diffuse small intestinal wall in up to 70% of cases.
thickening of the muscularis, propria, and submucosa.
Mesenteric lymphadenopathy is also common and has Staging
been reported in 45–80% of affected cats.
A cytologic or histologic assessment of a needle aspirate As in canine lymphoma, beyond those initial diagnostics
or needle biopsy samples from intestinal masses, enlarged performed to establish the diagnosis of lymphoma,
lymph nodes or other abnormal‐appearing organs is additional diagnostics should be considered as part of
essential to establish a diagnosis. Endoscopic, laparoscopic complete staging.
or incisional biopsy achieved by laparotomy may also be A complete blood work‐up including a CBC with dif­
performed. Full‐thickness GI biopsies best distinguish ferential blood cell count, serum biochemistry profile,
inflammatory bowel disease from lymphoma and will urinalysis, and FeLV/FIV screen should be completed on
differentiate a high‐ or low‐grade intestinal lymphoma. all cats. While most cats will have an unremarkable blood
profile, this is useful to evaluate for the presence of other
Mediastinal Lymphoma co‐morbid conditions.
For cats with mediastinal lymphoma, a diagnosis can be A bone marrow aspirate is indicated in cats with blood
established via survey thoracic radiographs followed by dyscrasias to confirm the presence of lymphoma and
thoracocentesis with cytologic examination of the fluid. rule out other etiologies. Results of a bone marrow