Fraction of neoplastic cells in breast cancer samples - Correction for theoncogene amplification test

OBJECTIVE: To develop the necessary correction for the polymerase chain rea ction-based oncogene amplification test applied to paraffin-embedded tissue sections. STUDY DESIGN: The theoretical basis for making the correction in test resul ts and for determining the neoplastic cell fraction was clarified, and a me thod for microscopic sampling was developed. The cell count bias was correc ted by applying an equation by Ebbeson and Tang and using two adjacent tiss ue sections of different thickness, cut from the block from which DNA was i solated. RESULTS: There was no need to determine the absolute thicknesses of the sec tions. Section thickness, as a relevant feature, teas cancelled out in deve loping the formula for estimating the cell fraction. The correction was app lied in practice, and when tested on 10 breast cancer samples, the correlat ion between amplification estimates from two observers was good (r = .96). CONCLUSION: This method is valuable for interpreting the test results based on paraffin sections and for developing simpler quantitating methods for s pecial test applications. The study also showed that amplifications may be more common than expected on the basis of the crude results of this type of test.