Immunophenotypic analysis of feline haemolymphatic neoplasia using flow cytometry

Abstract

Tissues from 17 cats with suspected haemolymphatic neoplasia were analysed using phenotypespecific monoclonal antibodies (MAbs) and flow cytometry. Eight of the cases were also classified according to the French-American-British (FAB) system for acute leukaemias and were characterised by cytochemical staining. Phenotypes identified by the panel of MAb employed here included T lymphocyte, CD4+ lymphocyte, CD8+ lymphocyte, undifferentiated lymphocyte, erythroid or myeloid. By combining the cytological diagnosis of neoplasia with the phenotype, a precise diagnosis was obtained in 15 of the 17 cases. Of the 15 cases successfully phenotyped, eight were T-cell, two were B-cell, one was myeloid, two were erythroid, and two were mixed erythroid and myeloid. Two samples that did not react with the panel of MAb were determined at necropsy to be of non-haemolymphatic origin. Expression of feline leukaemia virus (FeLV) by neoplastic cells was demonstrated in three of seven FeLV-positive cats. The lack of a B-lymphocyte-specific MAb was the most significant deficit in the antibody panel and precluded conclusive identification of B-cell leukaemias. The FAB classification provided a more objective means to identify myelodysplastic syndrome versus myeloproliferative disorder. Cytochemical staining confirmed flow cytometric results in non-lymphoid neoplasias but otherwise did not refine the phenotypic diagnosis made by flow cytometric analysis. In the cases presented here, immunophenotyping with flow cytometry and our panel of MAbs, accurately identified lymphoid versus non-lymphoid neoplasia, as well as single and mixed lineage myeloproliferative disorders.