Abstract
CASE SUMMARY: An 11-year-old male castrated domestic shorthair cat presented with increased respiratory effort, pleural effusion, lymphadenopathy, lethargy and decreased appetite with weight loss. A diagnosis of T-zone lymphoma was made from histopathology of an extirpated popliteal lymph node that had a marked paracortical expansion of small lymphocytes and prominent high endothelial venule proliferation. T-cell receptor gamma (TRG) molecular clonality PCR yielded a clonal rearrangement and immunohistochemistry demonstrated that the neoplastic lymphocytes expressed CD3 and did not express CD20. The cat was initially treated with two doses of intravenous vincristine and oral prednisolone followed by oral chlorambucil. The pleural effusion, lymphadenopathy, lymphocytosis, abdominal organomegaly and lethargy resolved, and the cat's appetite and body weight returned to normal. At the time of manuscript submission, the cat continued to do well, more than 24 months after presentation. RELEVANCE AND NOVEL INFORMATION: T-zone lymphoma is a common indolent lymphoma in dogs, but it has only been histopathologically described in one cat before this report. This is the first report to describe the clinical presentation, clinicopathologic findings and outcome for a cat with T-zone lymphoma.