INTERPHASE CYTOGENETIC ANALYSIS OF CULTURED PLEOMORPHIC ADENOMAS WITHA NORMAL KARYOTYPE

A subgroup of pleomorphic adenomas of the salivary glands is character ized by apparently normal stemline karyotypes. In this investigation w e have used FISH to study whether clonal translocations involving chro mosomes 8 and 12 might have escaped detection with conventional cytoge netic analysis. Whole chromosome painting probes for chromosomes 8 and 12 were hybridized to interphase nuclei from 22 cytogenetically norma l pleomorphic adenomas. In 20 of the 22 cases the majority of the nucl ei (75-93%) showed two hybridizing chromosome 8 and chromosome 12 doma ins of equal size, indicating the presence of two intact copies of eac h of these chromosomes. Evidence of clonal translocations was only det ected in two tumors. These findings show that in the vast majority of adenomas with a normal karyotype we can exclude the possibility of an abnormal non-dividing or very slow growing, and thus undetected, tumor cell population in vitro. Our data provides further evidence to suppo rt the existence of a subgroup of pleomorphic adenomas with a normal k aryotype.