Further analyses of the evolutionary characteristics of a sequentially studied human malignant mesothelioma

The present findings allow two important conclusions. First, there is often a long-lasting chromosomal instability of the modal population in mesotheliomas and even in advanced stages of tumor progression a lack of definite stemline karyotype. Second, there is often, even in late stages, a generation of new variant cells. They lack a clonal relationship to the cells of the modal group and are probably generated from a pool of transformed but chromosomally not grossly abnormal cells. These conclusions are in line with findings in two recently published new cases of mesotheliomas and they also fit with observations in ongoing experiments on normal cells exposed to various concentrations and chemical compositions of asbestos. Asbestos, thus, seems to play a key role for the unusual evolutionary pattern in mesotheliomas.