Detection of EGFR and KRAS mutations in fine-needle aspirates stored on Whatman FTA cards: is this the tool for biobanking cytological samples in the molecular era?

Background: The aims of this study were to compare the quality of DNA recovered from fine-needle aspirates (FNAs) stored on Whatman FTA cards with that retrieved from corresponding cell blocks and to determine whether the DNA extracted from the cards is suitable for multiple mutation analyses.

Methods: FNAs collected from 18 resected lung tumors and cell suspensions from 4 lung cancer cell lines were placed on FTA Indicating Micro Cards and further processed to produce paired formalin-fixed paraffin-embedded (FFPE) cell blocks. Fragment analysis was used for the detection of EGFR exon 19 deletion, and direct sequencing for detection of EGFR exon 21 L858R mutation and exon 2 deletion of KRAS. Corresponding FFPE tissue sections from 2 resection specimens were also tested.

Results: Analyses were successful with all FNAs and lung cancer-derived cell lines collected on cards. Polymerase chain reaction failed in 2 cell blocks. For FNAs collected on cards, 5 cases showed EGFR and 3 showed KRAS mutations. Eleven cases were wild type. With cell blocks, 4 cases were found to harbor KRAS and 4 harbored EGFR mutations. All lung cancer-derived cell lines tested positive for their respective mutations, and there was complete agreement between card and cell block FNA samples for EGFR exon 21. For EGFR exon 19, 1 of 18 cases showed discordant results between the card and cell block, and for KRAS 1 of 17. The two resection specimens tested gave concordant results with the FTA card.

Conclusions: Storage of cytologic material on FTA cards can maximize and simplify sample procurement for multiple mutational analyses with results similar to those from cell blocks.