The use of archival frozen tumor tissue imprint specimens for fluorescence in situ hybridization

Fluorescence in situ hybridization for the detection of gene amplification or deletion has great promise as a method of providing diagnostic or prognostic information from tumor specimens. Fine needle aspiration samples or tumor tissue imprints are much easier to use and provide better results than paraffin sections, however, these materials are rarely archived and it may take many months to accumulate enough specimens for a study. Archival breast carcinoma tumor tissue samples, some stored frozen for several years, were used to prepare tumor tissue touch imprints on glass microscope slides. The imprints were subjected to fluorescence in situ hybridization analyses utilizing a biotin-dUTP-labeled genomic DNA probe for the cyclin D1 gene (CCND1/PRAD1) and a digoxygenin-labeled chromosome 11 alpha-satellite probe to control for chromosomal copy number. Amplification of CCND1 was easily detectable in frozen tissue imprints. The results indicate that both cytologic morphology and hybridization capacity are well preserved in archived frozen tissue and easily permit its use for in situ hybridization experiments. The ability to use stored frozen tumor tissue for molecular morphologic analysis should allow more rapid assessment of fluorescence in situ hybridization as a potential adjunct for tumor analysis by the surgical pathologist.