Use of fluorescent in situ hybridization to detect aneuploidy in cervical dysplasia

Fluorescent in situ hybridization (FISH) with alpha satellite DNA probes for chromosomes 11 and X were applied to normal, atypical, and dysplastic cervical-vaginal cytology smears to evaluate the detection of hyperploidy in suspected abnormal cells. Forty-six cases were obtained from fixed archival material. Eight cases with a morphological diagnosis of within normal limits (WNL) were directly selected to use as controls. The other 38 cases were blinded as study cases. These included five WNL, six ASCUS, six SIL-LG, 16 SIL-HG, four invasive squamous cell carcinomas, and one case of adenocarcinoma of the cervix. Cells with chromosome copy numbers suggesting hyperploidy (3-4 signals per chromosome specific probe) were found more often in higher grade dysplasia (Bethesda class SIL-HG) cases and less often in lower grade lesions (SIL-LG). All cases morphologically diagnosed as WNL were found to have normal copy number except for one control case which was hyperploid and, upon reexamination of the original slides, was upgraded from normal to atypical squamous cells of undetermined significance (ASCUS). Our FISH results are similar to those of previous studies involving flow cytometry and morphometric cytometry in which changes in ploidy correlated with progression toward higher grade lesions. However, FISH with enumeration probes offers a higher resolution view of the genome than is possible with flow cytometry or morphometry by allowing detection of specific chromosome changes in small numbers of affected cells in a routine cervical smear, and it may have the capacity to detect those cases in which progression toward high grade dysplasias is more likely.