Chromosomal characteristics of malignant lymphoma in northern pike (Esox lucius) from the United States

Chromosome analyses were performed on tumor cells and normal hematopoietic cells of northern pike bearing malignant lymphomas. The normal pike karyotype contains 50 acrocentric chromosomes, among which the sex chromosomes are not identifiable by available techniques. Metaphases from 19 primary lymphomas showed a consistent pattern of chromosome anomalies consisting of 1 submetacentric marker, 1 minute marker, and 3 to 5 pairs of smaller-than-normal chromosomes, set within a mode of 50 and a range of 46 to 54. Occasional cells had 2 identical submetacentric markers. Cells from presumptively normal renal hematopoietic tissue in 41 lymphoma-bearing pike showed the euploid karyotype, with the exception of 2 cases in which some cells with the neoplastic pattern were found. This probably indicated occult neoplastic involvement of renal hematopoietic tissue, in spite of the absence of histological evidence of involvement. In many cases, some of the cells taken directly from lymphomas bore the normal karyotype. It is not known whether these cells were reactive lymphoid cells or lymphoma cells that had not developed those anomalies typically associated with the tumors. The findings do not permit a conclusion regarding agent versus cellular transmission. However, the pike lymphoma is an excellent example of a neoplasm with a karyotypic "signature."