Intestinal lymphoma of granular lymphocytes in a fisher (Martes pennanti) and a Eurasian otter (Lutra lutra).

Intestinal lymphoma of granular lymphocytes was diagnosed in a 6-year-old fisher (Martes pennanti) and a geriatric Eurasian otter (Lutra lutra). Clinical signs included lethargy and inappetance in both animals and vomiting and occasional diarrhea in the fisher. The diagnosis in both cases was made using cytology of fresh tissue, histology of fixed tissues, and immunohistochemistry. Granules were seen most clearly on cytologic examination of direct impressions from fresh tissue. Because granules were absent in most histologic sections, cytology of fresh tissue was essential for the diagnosis. Immunohistochemistry determined that the neoplastic cells had positive membranous immunoreactivity to CD3 and were negative for CD79a, which was consistent with alimentary T-cell lymphoma. The disease course in both animals was presumed to be aggressive, with rapid progression of clinical signs, high mitotic index and effacement of local intestinal architecture in both cases, and metastatic disease in the fisher. To the authors' knowledge, this is the first report of lymphoma of granular lymphocytes in a fisher and a Eurasian otter.