[419] Double EGFR Mutation in Pulmonary Adenocarcinoma Detected by ThinPrep® Preparation

H Itoh, T Itoh, A Serizawa, N Kato, C Inomoto, RY Osamura. Tokai University School of Medicine, Isehara, Kanagawa, Japan

Background: Mutation on exon 21 and deletion on exon 19 are related to non-smokers and adenocarcinoma of the lung are expected to response for targeted therapy by gefitinib and erlotinib. We have been using ThinPrep®(Hologic Inc.) to combine morophology and gene mutational analysis. Recently, two cases have been highlighted to show double EGFR mutation.
Design: ThinPrep® preparation was made from adenocarcinoma of the lung(four cases of bronchial brushing and four cases of fresh tissue subjected to frozen section diagnosis). After confirming adenocarcinoma or bronchiole-alveolar carcinoma(BAC), the carcinoma cells in fixative by ThinPrep® were subjected to PCR and subsequent direct sequencing for the mutational analysis of EGFR exons 18-21.
Results: Six cases were of wild type without any mutations in exons 18,19,20,21. Two cases showed double mutations, cases #1 with delE746-A750 and L858R, and cases #2 E709K and G719A on exon 18.
Conclusions: Formalin-fixed paraffin embedded(FFPE) materials are well known to be appropriate samples for mutational analysis. Our present study has shown the cells in the fixative(methanol-based) for ThinPrep® can preserve multiple mutations in the same tumor. Multiple EGFR mutations in the same case are rare and account for 34cases /1272 cases (2.8%) in large series(SRL Inc.). Case #1 with two common mutations, delR746-A750 and L858R is expected to respond well for the targeted therapy.
Category: Cytopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 49, Wednesday Afternoon

 

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