EGFR-gene analysis on cytological specimens of non-small-cell lung cancers
© Savic et al; licensee BioMed Central Ltd. 2007
Published: 14 March 2007
The diagnosis of lung cancer is often based on cytology alone. The relative paucity of tumor cells in these specimens is a challenge for the analysis of epidermal growth factor receptor (EGFR) gene mutation and EGFR gene copy number to select for treatment with EGFR-tyrosine kinase inhibitors. Here, we tested whether such EGFR gene analyses are feasible on cytological specimens of non-small-cell lung cancers (NSCLC).
We analyzed 87 Papanicolaou stained cytological specimens from patients with NSCLCs (51 adenocarcinomas, 27 not further defined NSCLCs, 8 squamous cell carcinomas and one neuro-endocrine carcinoma). The carcinoma cells were selectively dissected from the cytological specimens under visual control using laser microdissection in combination with a laser pressure catapulting system (PALM®). We sequenced the exons 18–21 of the EGFR gene. EGFR gene copy number was evaluated by fluorescence in situ hybridization (FISH) under visual control using relocation software. A FISH positive result was defined according to the criteria defined by F. Cappuzzo et al. on biopsies of NSCLCs . FISH results of cytological specimens were compared with the FISH results on corresponding biopsies.
DNA sequencing was successful in 79 of the 87 specimens (91%). Three adenocarcinomas showed EGFR-gene mutations (3.8%). 44 of 65 cancers (68%) were FISH positive on the cytological specimens as compared with only 2 of 9 biopsies (24%).
EGFR gene sequencing and FISH are well applicable to cytological specimens from lung cancers in diagnostic routine using laser microdissection and automated relocation. The high FISH positive rate of 68% suggests that the criteria for a FISH positive result suggested by Cappuzzo et al. need to be adjusted for cytological specimens.
This article is published under license to BioMed Central Ltd.