EGFR analysis on scrapings from cytology smears in lung carcinoma, an effective alternative to testing on trucut biopsies. Issue 10 (25th August 2021) - Mohan, Anish A.
Abstract: Background: Lung carcinomas are a leading cause of cancer morbidity and mortality. Many cases present at an advanced stage of disease where definitive treatment by surgical resection is not feasible. Molecular testing using materials derived from minimally invasive procedures aid in targeted therapy with least iatrogenic burden to the patient. Methods: Cases diagnosed as non‐small cell lung carcinoma (NSCLC) on cytology were included in the study. Scrapings from the smears with adequate tumor cell load were submitted for molecular testing. The DNA was extracted and quantified. Mutations in exons 18, 19, 20, and 21 of the EGFR gene were detected using Sanger sequencing. DNA quantity and EGFR mutation status on equal number of consecutive trucut biopsy specimens were also analyzed. Results: Seventy cases of NSCLC tested for EGFR mutation had a median DNA concentration of 40.2 ng/μl and 31% cases showed mutation. Majority of mutations (14/21, 66.66%) were identified in exon 19. Among 70 trucut biopsy samples, DNA concentration was 41.42 ng/μl and 30% cases showed mutation. No significant difference was seen in DNA quantity and EGFR mutation between cytology smears and trucut biopsies. Conclusion: EGFR testing on cytology smears provides adequate DNA yield with minimal invasiveness and is equally effective as biopsies. Testing on samples like pleural effusion allows for concomitant diagnosis, staging, and molecular testing in one procedure. Tests done on the smears rather than on cell block or trucut biopsies ensures superior quality DNA from the tumor cells as they are unexposed to cross linking formalin fixative.