Abstract
The EGFR gene mutation test is very important for selecting the optimal lung cancer molecular target therapy. Many of the analyzed specimens are formalin-fixed paraffin-embedded. However, DNA may become fragmented under such formalin fixation conditions, which thus can result in measurement errors. From August 2014 to July 2015, we obtained touch imprint cytology (TIC) specimens from 18 patients intraoperatively in our hospital and performed the EGFR gene mutation test. We then compared the DNA concentration and the proportion of mutations between the FFPE specimens and the TIC specimens, and also evaluated DNA quality by real-time PCR analysis. The FFPE specimens were found to demonstrate poorer DNA quality than the TIC specimens. As a result, EGFR gene mutations were found in 11 patients, while no mutations were found in 7 patients. There was no difference in the presence or absence of mutations according to specimen type. The mutated region did not show any differences in the specimen type. A higher proportion of mutations was found in the TIC specimens; in contrast, the DNA concentrations tended to be lower. In addition, the DNA quality index tended to be higher in the TIC specimens. Moreover, alcohol-fixed specimens demonstrated better DNA quality than the formalin-fixed ones. Finally, for TIC specimens, it is possible to selectively recover tumor cells. We therefore recommend the use of TIC techniques for performing the EGFR gene mutation test, which demands high precision and rapidity.
