DETECTION OF HIDDEN STRUCTURAL REARRANGEMENTS BY FISH IN PLEOMORPHIC ADENOMAS

Previous cytogenetic analysis of pleomorphic adenomas of the salivary glands has revealed a subgroup of tumors with interstitial deletions o f 8q with breakpoints at q12 and q21-23. In this paper we have re-exam ined four adenomas with confirmed or suspected deletions of 8q by FISH , Painting of interphase nuclei and metaphase chromosomes with whole c hromosome libraries revealed that in each of the four cases the delete d chromosome 8 material was found inserted or translocated onto other chromosomes. In two of the cases we were also able to resolve several other complex rearrangements. Our FISH data thus suggest that gross de letions of 8q do not occur in pleomorphic adenomas. These observations are of crucial importance for the molecular interpretations of the 8q 12 rearrangements. The fact that all rearrangements with breakpoints a t 8q12 seem to be translocations or insertions strongly indicates that they involve a similar molecular mechanism. Our findings illustrate t hat chromosome painting is a valuable and useful adjunct to convention al cytogenetic analysis of solid tumors. (C) 1995 Wiley-Liss, Inc.