Adjusting interphase FISH results in epithelial tissue sections to whole cell complement

OBJECTIVE: To derive an equation to compensate for the discrepancies betwee n whole cell preparations and tissue sections for more accurate enumeration of fluorescence in situ hybridization (FISH) signals per cell. STUDY DESIGN: Mean centromere signal counts in touch preparations and corre sponding 4-6-mum sections of paraffin-embedded tissue were calculated. Mean widest nuclear diameters were also determined from the tissue sections. Th e observed data were analyzed to define the volumetric relationships betwee n tissue sections and whole cell preparations. RESULTS: Analysis of results from six lung specimens yielded an equation th at approximates whole versus sectioned nuclear volume and permits accurate quantification of mean FISH signal count in histologic sections, as follows : Signals(whole) = Signals(section) * [(D + 1.5t)/3.62t], where t is section thickness and D the mean widest diameter. The applicabil ity of this equation teas confirmed in 14 other epithelial specimens. CONCLUSION: Extrapolation of FISH signal count in sectioned nuclei to the w hole cell preparation condition is possible by application of the proposed, experimentally derived correction factor. It should improve the accuracy o f interphase FISH in tissue sections.