EGFR mutation testing using archival-stained smears in non-small cell lung carcinoma

Area of Science:

• Oncology
• Molecular Diagnostics
• Pathology

Background:

• Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) improve outcomes for patients with EGFR-mutated lung cancer.
• Lung cancer is often diagnosed at a metastatic stage, necessitating analysis from limited tissue samples.
• Cytological materials and small biopsies are frequently used for diagnosis.

Purpose of the Study:

• To compare the accuracy of EGFR mutation analysis between cytological samples, small biopsies, and resections.
• To evaluate the impact of specimen type and preparation on EGFR mutation detection.

Main Methods:

• Review of archival material from 300 unpaired specimens (84 resections, 83 small biopsies, 133 cytological).
• Analysis of EGFR mutation rates across different sample types and preparation methods (cell blocks, smears).
• Investigation of tumour cell percentage, DNA content, and TTF-1 immunoreactivity influence.

Main Results:

• EGFR mutation rates were comparable across cytology, small biopsies, and resections (P > 0.05).
• Specimen preparation methods (slides vs. cell blocks) and staining techniques (MGG vs. Pap) influenced EGFR mutation detection.
• Negative TTF-1 immunoreactivity was associated with a lower likelihood of EGFR mutation (P < 0.05).

Conclusions:

• Cytological materials are a viable and accurate source for EGFR mutation analysis in lung cancer.
• These findings support the use of cytology for guiding TKI therapy selection.