Common feline cancers (Proceedings)

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Common feline cancers (Proceedings)

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Apr 01, 2010

Lymphoma

Lymphoma (LSA) is one of the most common feline malignancies, comprising approximately 30% of all reported tumors. While not curable, LSA may respond quite well to therapy and can be a very satisfying neoplasm to treat.

Signalment

The age of cats affected has increased over the past 10 years, due to the decline in FeLV+ cases. Middle-aged to older cats are mainly affected. Young cats with LSA are often FeLV+.

Etiology

FeLV is linked with most forms of LSA except the GI form. FeLV+ LSA is a T cell variant and occurs in younger cats (2 to 4 years). The risk of developing LSA is increased by 5x with FIV infection and by 77x with FeLV and FIV co-infection. FeLV can directly cause malignant transformation, while FIV is thought to predispose to lymphoma via immune dysfunction. Inflammatory bowel disease may ultimately progress to lymphoma, but this theory is not proven.

History



Presenting complaints in cats depends on the form of LSA affecting the patient. As the GI form is the most common, signs include any or all of the following: weight loss, inappetance, lethargy, vomiting, and/or diarrhea. Multicentric cases will usually be ill and have enlarged lymph nodes ("lumps" noted by owner). Mediastinal LSA causes dyspnea (from the mass or secondary pleural effusion) and/or regurgitation (also a mass effect). Extranodal LSA also will present with concerns based on location: sneezing/epistaxis for nasal, paresis/paralysis for CNS, systemic illness with the renal form, and blindness or discomfort in ocular cases.

Diagnostic evaluation/staging

Depending on the form of the cancer, the diagnosis of LSA in cats may be achieved with fine needle aspirate (FNA) or may require histopathology. Situations where biopsies are indicated include the GI form that is microscopic and diffuse, multicentric lymphoma (peripheral lymph nodes can be enlarged for a number of non-neoplastic causes which may not be cytologically distinguishable), nasal and cutaneous LSA.

As LSA is almost always a systemic disease, staging to determine extent of disease is important for prognosis and monitoring response to therapy. Many of the specific forms of LSA do not stay isolated to the primary location. For example, renal LSA may progress to involve the CNS, and spinal LSA frequently involves the bone marrow. However, staging may not be indicated in cats that have a very poor prognosis at diagnosis (eg FeLV+ mediastinal LSA, leukemia).

Diagnostic evaluation of cats with LSA includes a complete blood count, serum chemistry profile, urinalysis, FeLV/FIV testing, bone marrow aspirate, thoracic and abdominal radiographs and abdominal ultrasound. Clinical substage is based on symptoms: substage a is asymptomatic, substage b correlates with an ill patient.

Prognostic factors

Unlike in dogs, there are not many prognostic factors in cats that help to predict which cats will respond to therapy. The anatomic location of the lymphoma may be prognostic; some forms may respond better than others. Such information is somewhat unclear due to most studies grouping together cats with various forms in the remission/survival analysis, and due to small numbers of cats in the studies. Other prognostic factors include clinical substage (b does worse) and FeLV status (+ have decreased remission times). One of the most prognostic findings, which unfortunately cannot be assessed prior to treatment, is response to therapy (cats that go into remission have greatly prolonged survivals).