Lymphosarcoma in the laboratory woodchuck (Marmota monax).

From 1979 to 1999,28 cases of lymphosarcoma were identified in the Cornell University woodchuck colony (prevalence rate: 152/100,000/yr). The prevalence of lymphosarcoma was similar in woodchucks not infected with the woodchuck hepatitis virus (WHV) and in chronic carriers of WHV. Males (13) and females (15) alike were affected (mean +/- SD age 4.7 +/- 2.92 years; range, 0.5 to 9 years). On the basis of the major organ system involved, woodchuck lymphosarcoma was classified as multicentric (12 cases, 43%), alimentary (5 cases, 18%), cranial mediastinal (5 cases, 18%), and miscellaneous (6 cases, 21%). A cutaneous form was not observed. Morphologic criteria similar to those of the Kiel classification were used for light microscopic classification. All Kiel categories-except the immunoblastic form-were found: 17 cases (61%) were centroblastic, and 6 were lymphocytic (21%). Other categories (centrocytic and plasmacytoid) were recognized less frequently. Immunophenotyping of 27 cases revealed 15 (56%) B cell (CD3-/CD79a+ or CD3-/BLA.36+), 7 (26%) T cell (CD3+/CD79a-/BLA.36-), and 5 (18%) non-T non-B cell (CD3-CD79a-/BLA.36-) lymphosarcomas. Lymphosarcoma in woodchucks develops at a higher rate than that observed in humans or companion animals, and WHV infection has no effect on prevalence. The anatomic and Kiel classification used in domestic species also can be used in woodchucks. Commercially available alpha-CD3, alpha-CD79a, and alpha-BLA.36 antibodies were useful for immunophenotyping woodchuck lymphosarcomas.