Tumour cell hybridization and metastasis revisited

This article reviews a long-standing hypothesis that metastases might be in itiated through the generation of hybrids between primary tumour cells and tumour-infiltrating leucocytes such as macrophages. In this concept the hyb rids become metastatic through expression of the leucocyte motility phenoty pe. A history of the hybrid hypothesis is presented along with recent evide nce on how macrophage x tumour cell hybridization could account for some of the most defining characteristics of metastatic cells: aneuploidy, enhance d motility, aberrant glycosylation and, particularly seen in melanoma, phen otypic diversity. (C) 2000 Lippincott Williams & Wilkins.