Chromosomal doubling: the significance of polyploidization in the development of human tumors: possibly relevant findings on a lymphoma.

Recent molecular evidence points to defects in cell cycle checkpoints as one of the most important events in the transformation of normal to malignant cells. A byproduct of, if not a critical step brought about by, these defects is the occurrence of polyploidization; near-tetraploid and near-octoploid cells are a common feature of cancers, and the neoplastic stemline may itself attain a high (e.g., near-tetraploid) value. This short review cites cases in which polyploidization is frequent, even at an early stage of tumor development, and considers the probability that, once a high stemline has arisen, there is increased instability with the likelihood of further chromosome changes. A possible example of the latter is a lymphoma in which tetraploid and hypotetraploid metaphases were found, the latter, interestingly, showing an apparently preferential loss from tetraploidy of chromosome 10. It appears, therefore, that a stemline was emerging consequent to (a) chromosome doubling resulting in tetraploid cells, and (b) the appearance of a hypotetraploid line in which chromosome 10 was under-represented. Alternately, there might have been a repeated loss of chromosomes from tetraploid cells that preferentially included chromosomes 10.