Cytogenetic analysis in nine leukaemic cats.

Eight of nine leukaemic cats had chromosomal abnormalities. The major differences between the healthy, FeLV-negative control cats and the leukaemic cats were the increased number of hyperdiploid cells and the presence of double minute or morphologically abnormal chromosomes in the leukaemic cats. Three leukaemic cats had cells with double minute chromosomes, while no normal cats had cells with double minute chromosomes. Tetrasomy or trisomy most frequently involved chromosomes C2 and B4. Monosomy was most common in chromosomes A3, C2, D4, E3 and F2. Chromosome abnormalities were also observed in bone marrow cells from two of three healthy, FeLV-positive cats and both cats with thymic lymphosarcoma. Increased numbers of hyperdiploid cells, double minute chromosomes and trisomy of C2 were the most important findings. No correlations between cytogenetic findings and diagnosis or prognosis were found. Additional research is necessary to determine the significance of chromosome aberrations in cells from healthy, FeLV-positive cats. If these changes prove to represent early neoplastic transformation, chromosome analysis could provide valuable diagnostic information and identify patients that might benefit from early chemotherapy. Results of this limited study indicate (1) chromosome aberrations are common in leukaemic cats, (2) chromosome changes are not completely random, (3) direct bone marrow technique for chromosome analysis is generally preferable in leukaemic cats and (4) the cat appears to be a good model in which to study chromosomal abnormalities in leukaemia, though more research is needed.