Specificity of the involvement of chromosomes 8 and 12 in human mixed salivary-gland tumours.

Using the G-banding technique the chromosomal patterns in 10 in vitro-cultured human mixed salivary gland tumours were studied. When surveying the results from the present 10 adenomas together with previous results from 31 adenomas, the following characteristic features were found. Mixed tumours probably always originate with a normal diploid stemline. This stemline type was also found to predominate during progression. However, about 41% of the tumours showed abnormal stemlines characterized by highly specific, usually structural, clonal aberrations. The deviations in these abnormal stemlines seemed to preferentially affect certain chromosome types, viz. Nos. 8 and 12. This non-random pattern of deviations - not found earlier in either benign or malignant tumour types in man - indicates that certain regions of, especially, chromosomes 8 and 12 are selectively affected in mixed tumours. Among other things, changes of gene dosage and/or oncogene activation are mentioned as factors possibly influencing the characteristics of this non-random pattern.