USE OF FLUORESCENT INSITU HYBRIDIZATION FOR DEOXYRIBONUCLEIC-ACID PLOIDY ANALYSIS OF PROSTATIC ADENOCARCINOMA

Fluorescent in situ hybridization using 2 chromosome specific centrome re probes was evaluated as a method of ploidy analysis in touch prepar ations from 50 radical prostatectomy specimens. Tumors were classified as aneuploid by fluorescent in situ hybridization when nuclei had an abnormal copy number (aneusomic) for either chromosome centromere 8 or 12. Tetraploid tumors were defined as those with 4 copies (tetrasomic ) of chromosome centromeres 8 and 12. The fluorescent in situ hybridiz ation ploidy patterns were compared to the deoxyribonucleic acid (DNA) ploidy patterns subsequently obtained by flow cytometry on the same t issue following paraffin embedding. Concordant fluorescent in situ hyb ridization and flow cytometry ploidy classification was obtained in 82 % of the cases (p less-than-or-equal-to 0.0001). Of 7 aneuploid tumors 3 were identified by both methods. Trisomy 8 was detected by fluoresc ent in situ hybridization in 3 cases that were classified as DNA diplo id (2 tumors) and DNA tetraploid (1 tumor). Conversely, flow cytometry detected aneuploidy (hypotetraploidy) in 1 tumor when the fluorescent in situ hybridization results were consistent with tetraploidy. Overa ll, fluorescent in situ hybridization was more sensitive in aneuploidy detection (6 of 7 cases) than flow cytometry (4 of 7). Of 19 tetraplo id cases 5 had discordant fluorescent in situ hybridization and flow c ytometry results. However, all 5 cases contained low levels of tetrapl oidy and the discrepant results were most likely due to the limits of precision of 1 or both methods. In conclusion, we demonstrated that fl uorescent in situ hybridization ploidy analysis can be rapidly perform ed on fresh touch preparations of prostate tissue. This preliminary st udy demonstrates that the ploidy result determined by fluorescent in s itu hybridization correlates well with that obtained by flow cytometry . More complete fluorescent in situ hybridization studies of prostate carcinoma will require additional probes for other chromosomes.