Cytogenetical observations in 100 human benign pleomorphic adenomas: specificity of the chromosomal aberrations and their relationship to sites of localized oncogenes.

Using short-term cultures, the chromosomes in 19 human benign pleomorphic adenomas were studied by banding methods. The results were considered together with 81 previously reported adenomas. This survey showed that 53% of the 100 adenomas had a normal stemline. However, almost all cases with a normal stemline contained variant cells. Those with trisomy 7, trisomy 8, or loss of an X chromosome had progressional importance, as well as those variant cells containing markers composed of certain specific chromosome segments. In 47 adenomas a total of 50 abnormal stemlines were seen. They could be divided into four groups: (a) A large group with chromosome 8 involvement, usually translocation of the segment distal to 8q12; (b) A small group with chromosome 12 involvement, mostly translocation of the segment distal to 12q13-15; (c) A small group with translocations and/or deletions affecting a distal segment of either the short or the long arm of No. 3; (d) A small and heterogenous group with abnormalities which were related to those seen in variant cells from cases with a normal stemline. Comparisons between sites of localized oncogenes and deduced break points for markers in stemlines with only structural changes revealed accordance in 75% of the cases (33/44). It is noteworthy that almost 50% of the abnormal stemlines showed a proximal long-arm rearrangement of No. 8 that could fit with activation of the oncogene c-mos.