HISTOLOGIC CLASSIFICATION AND IMMUNOPHENOTYPE OF LYMPHOSARCOMAS IN CATS WITH NATURALLY AND EXPERIMENTALLY ACQUIRED FELINE IMMUNODEFICIENCY VIRUS-INFECTIONS

Lymphosarcoma (malignant lymphoma) is the commonest hematopoietic tumo r in the cat. Many cases are associated with feline leukemia virus (Fe LV) infection, but epidemiologic and experimental data suggest that fe line immunodeficiency virus (FIV) may also have a role in lymphomagene sis. In this paper, we describe the clinical presentation, histologic classification, and immunophenotype of lymphosarcoma in eight domestic cats with natural or experimental FN infections. The tumors were ofte n of unusual distribution, with the majority of cases conforming to th e least common anatomic classification of ''miscellaneous.'' Histopath ologic and immunophenotypic analysis using a panel of anti-cat and cro ss-reactive anti-human monoclonal and polyclonal antibodies identified seven of these tumors as high-grade B cell lymphomas of the centrobla stic or immunoblastic subtypes. The remaining case was a T-cell tumor associated with a concurrent FeLV infection. Our findings, together wi th the results of an analysis of FIV proviral DNA in these tumors, ind icate that the B-cell lymphosarcomas were comparable to those observed in human and simian immunodeficiency virus infections and that the ro le of FIV in lymphomagenesis is indirect and related to the potential for malignant transformation during polyclonal B cell activation.