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In advanced non-small-cell lung carcinomas epidermal growth factor receptor (EGFR) and KRAS testing is often performed on cytology. Liquid-based cytology (LBC), which eliminates the need for slide preparation by clinicians, may be very useful. In 42 LBC DNA was extracted twice. One sample was obtained directly from CytoLyt solution, whereas the other DNA sample was derived after smear preparation and laser capture microdissection (LCM) of Papanicolaou-stained cells. EGFR and KRAS mutational analyses were performed by direct sequencing. On CytoLyt-derived DNA four EGFR (9%) and five KRAS (12%) gene mutations were found. When direct sequencing was performed after LCM, the rate of cases that displayed either EGFR or KRAS mutations increased from 21% to 40%. Although time-consuming, LCM makes direct sequencing highly sensitive even on LBC preparations containing only a few cells.

Currently, there is a trend towards an increasing use of liquid-based cytology (LBC) to diagnose non-small cell lung cancer. In this study, to detect epidermal growth factor receptor mutations, different molecular techniques were applied to LBC samples with and without laser capture microdissection (LCM). In 58 LBCs, DNA was extracted twice. One sample was obtained directly from CytoLyt solution, whereas the other DNA sample was derived after slide preparation and LCM of Papanicolaou-stained cells. The rate of mutant cases obtained by direct sequencing was discordant between CytoLyt-derived (10.3\%) and LCM-derived (17.2\%) DNA. However, the same mutant rate (17.2\%) was achieved on the matched samples by high-resolution melting analysis, fragment and TaqMan assays. Thus, LCM and direct sequencing may be replaced by more sensitive non-sequencing methods directly performed on CytoLyt-derived DNA, an easier and faster approach to improve epidermal growth factor receptor testing standardisation on LBCs.