INTERPHASE CYTOGENETIC ANALYSIS OF SINGLE-CELL SUSPENSIONS PREPARED FROM PREVIOUSLY FORMALIN-FIXED AND PARAFFIN-EMBEDDED TISSUES

Fluorescence in situ hybridization (FISH) provides a rapid and accurat e method for the detection of chromosomal aneuploidy. We have develope d a technique for the use of FISH on single cell suspensions produced from either formalin-fixed or paraffin-embedded tissues. Preparation o f such tissues involves sequential rehydration, enzymatic digestion to release single nuclei, and hybridization with a fluorescently labeled chromosome-specific centromeric probe. In a clinical setting formalin -fixed tissue from many tissue types is readily available for addition al retrospective study. FISH on formalin-fixed tissues is especially b eneficial in follow-up studies of cases involving termination after pr enatal diagnosis or patients with a malignant disease where previous r outine cytogenetics established the chromosomal aneuploidy. The use of this technique eliminates the biases of cytogenetic analysis due to c lonal selection in tissue culture, the low number of cells analyzed, a nd the restriction to only dividing cell populations. We have demonstr ated that this application of interphase cytogenetics to the study of various formalin-fixed tissues is amenable to the detection of chromos omal aneuploidies and has specific advantages over cytogenetic analysi s.