Detection of numeric abnormalities of chromosome 17 and p53 deletions by fluorescence in situ hybridization in pleomorphic adenomas and carcinomas in pleomorphic adenoma. Correlation with p53 expression.

Background: A fluorescence in situ hybridization (FISH) technique using specific DNA probes allows for the detection of chromosomal aberrations and gene deletions and gains, even in interphase nuclei in human solid tumors. A high frequency of aberrations of chromosome 17 and mutation of the p53 gene have been reported in some human tumors. The correlation of p53 expression with abnormalities of chromosome 17 and p53 gene deletion in salivary gland tumors has not yet been investigated.

Methods: The authors analyzed the numeric aberrations of chromosome 17 and p53 gene deletions in 11 paraffin embedded pleomorphic adenomas (PA) and 9 carcinomas in pleomorphic adenoma (CIPA), using FISH techniques. The centromere specific DNA probe for chromosome 17 and p53 cosmid DNA probe was used. The aberrations of chromosome 17 and p53 deletion were correlated with immunohistochemical detection of p53 protein.

Results: Monosomy 17 was detected in 30.8% of CIPA cells and 29.6% of PA cells, and polysomy 17 was detected in 19.6% of CIPA cells and 9.6% of PA cells. p53 protein expression was observed in 6 of 9 CIPA specimens (66.7%) and 2 of 75 PA specimens (2.7%). Deletion of the p53 gene was frequent in p53 protein positive specimens. A statistically significant correlation existed between p53 protein expression and polysomy 17 (P = 0.0417).

Conclusions: It was observed that loss of chromosome 17 may occur in PA before its transformation to carcinoma. p53 expression was frequently associated with deletion of the p53 gene as detected by FISH. Polysomy 17 was more frequent in CIPA than PA and was associated with mutation of p53.