Gastrointestinal (GI) (or alimentary) lymphoma is the most common form of lymphoma in cats1-3. Feline GI lymphoma is histologically
classified as low, intermediate or high grade according to the size and anaplasticity of the neoplastic lymphoid cells. Low-grade,
small cell, lymphocytic feline GI lymphoma is composed of small relatively well-differentiated neoplastic lymphocytes, while
high grade, lymphoblastic feline GI lymphoma is composed of large, poorly differentiated neoplastic lymphocyte. Clinical signs
of low grade GI lymphoma are often chronic in nature, reflecting the generally slow onset and progression of the disease and
commonly include weight loss, anorexia and lethargy with or without vomiting and diarrhea2-5. In contrast, high grade GI lymphoma
is a more acute and severe disease3. Anorexia, weight loss, palpable abdominal mass and an acute presentation due to intestinal
obstruction or perforation are common3. The epidemiology, presentation, diagnosis and staging of feline GI lymphoma are reviewed
Important Considerations For Diagnosis Of GI Lymphoma
Definitive diagnosis of gastrointestinal lymphoma requires histological evaluation of gastrointestinal tissue. Although biopsy
specimens can be obtained endoscopically or during exploratory laparotomy, recent evidence suggests full thickness gastrointestinal
biopsies are superior to endoscopic biopsies in differentiating GI lymphoma from IBD, especially in the small intestine which
is the most common site of feline GI lymphoma4. Further, histological evaluation of transmural intestinal biopsies along with
extraintestinal tissue (mesenteric lymph nodes and liver) is helpful in differentiating neoplastic from inflammatory disease6.
Indications for surgery in cats with GI lymphoma are gastrointestinal obstruction, gastrointestinal perforation or to obtain
biopsy samples of gastrointestinal and extraintestinal tissues (Richter). In most cases, chemotherapy is indicated following
resection of a focal mass as microscopic diffuse intestinal involvement or systemic spread is likely2.
Chemotherapy For Low Grade GI Lymphoma
Prednisone or prednisolone (5-10 mg PO q24hrs) and chlorambucil (2 mg PO q2-3 days or 15mg/m2 PO q24 hours for 4 consecutive
days, repeat every 3 weeks). The tendency for low grade lymphoma to be slowly progressive allows for outpatient treatment
with a less intense, oral chemotherapy protocol5. Most cats with low grade GI lymphoma respond favourably to prednisone and
chlorambucil therapy and experience extended survival times. Among 26 cats with low grade GI lymphoma treated with prednisone
and chlorambucil, 9 demonstrated complete, 16 partial and 1 no response to treatment with a collective median survival time
of 745 days5. In a separate study, 76% of cats (13/17) achieved complete remission with a median remission time of 18.9 months1.
It has been demonstrated that cats that achieve complete remission achieve longer survival times than cats that do not1,5.
However both groups of cats experience relatively long median survival times. Two recent retrospective reviews reported median
survival times of 587 and 897 days for cats that achieved complete remission and 125 and 428 days for cats that did not1,5.
The effect of chlorambucil regimen (alternate day versus high-dose pulse therapy) on median survival time has yet to be investigated.
Adverse effects of chlorambucil therapy are infrequent and include gastrointestinal signs and myelosuppression (neutropenia
and/or thrombocytopenia)1. A complete blood count (CBC) should be performed prior to initiation of therapy, one week after
the first dose of chlorambucil and every 2-3 weeks (alternate day chlorambucil regimen) or prior to each chlorambucil treatment
period (high dose pulse therapy chlorambucil regimen)3. Once complete remission is achieved and/or no leukopenia or trend
towards leukopenia is observed on serial CBCs over a few months, the frequency of CBC monitoring can be decreased to once
every 4-6 weeks3. Chlorambucil should be discontinued in cats with persistent or displaying a trend towards neutropenia or
thrombocytopenia3. Cats with low grade lymphoma that do not respond to or develop progressive disease in the face of prednisone
and chlorambucil therapy should be treated as per high grade lymphoma, described below.