The role of the cytopathologist in subtyping and epidermal growth factor receptor testing in non-small cell lung cancer: An institutional experience

EGFR analysis on scrapings from cytology smears in lung carcinoma, an effective alternative to testing on trucut biopsies

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.

Desmoglein 3 and Keratin 14 for Distinguishing Between Lung Adenocarcinoma and Lung Squamous Cell Carcinoma

Background

Lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) are the leading major histological phenotypes of all non-small cell lung cancer (NSCLC). In this study, the candidate genes and the potential tumorigenesis distinguishing between LUAD and LUSC were analyzed.

Methods

The present study investigated two microarray datasets (GSE28571 and GSE10245) downloaded from the Gene Expression Omnibus (GEO) database. A protein–protein interaction (PPI) network was applied to screen out the candidate genes. In addition, differently expressed genes (DEGs) between lung adenocarcinoma and lung squamous cell carcinoma of the two datasets were functionally analyzed by Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. R 4.0.2 was used to perform Kaplan–Meier analysis of DSG3 (desmoglein 3) and KRT14 (keratin 14) by analyzing the expression and clinical data from The Cancer Genome Atlas (TCGA) database.

Results

The results revealed that 47 DEGs of the two datasets were ascertained in our study. It was found that the DEGs were mainly involved in pathways related to p63 transcription factor network and validated transcriptional factor targeting TAp63, etc. Based on the analysis, we finally identified DSG3 and KRT14 as potential biomarkers for distinguishing between LUAD and LUSC. These results suggested that DSG3 and KRT14 could have the potential to play an important role in NSCLC patients, as diagnostic markers. At the same time, DSG3 or KRT14 indicated a worse prognosis in LUSC patients, which were associated with pathways relevant to the TRAIL signaling pathway and TNF receptor signaling pathway according to bioinformatic analysis.

Conclusion

The DSG3 and KRT14 have the potential to be used as diagnostic markers, which presented here may facilitate improvements in distinguishing between LUAD and LUSC in advanced NSCLC patients.

Best Practices Recommendations for Diagnostic Immunohistochemistry in Lung Cancer

Since the 2015 WHO classification was introduced into clinical practice, immunohistochemistry (IHC) has figured prominently in lung cancer diagnosis. In addition to distinction of small cell versus non-small cell carcinoma, patients' treatment of choice is directly linked to histologic subtypes of non-small cell carcinoma, which pertains to IHC results, particularly for poorly differentiated tumors. The use of IHC has improved diagnostic accuracy in the classification of lung carcinoma, but the interpretation of IHC results remains challenging in some instances. Also, pathologists must be aware of many interpretation pitfalls, and the use of IHC should be efficient to spare the tissue for molecular testing. The International Association for the Study of Lung Cancer Pathology Committee received questions on practical application and interpretation of IHC in lung cancer diagnosis. After discussions in several International Association for the Study of Lung Cancer Pathology Committee meetings, the issues and caveats were summarized in terms of 11 key questions covering common and important diagnostic situations in a daily clinical practice with some relevant challenging queries. The questions cover topics such as the best IHC markers for distinguishing NSCLC subtypes, differences in thyroid transcription factor 1 clones, and the utility of IHC in diagnosing uncommon subtypes of lung cancer and distinguishing primary from metastatic tumors. This article provides answers and explanations for the key questions about the use of IHC in diagnosis of lung carcinoma, representing viewpoints of experts in thoracic pathology that should assist the community in the appropriate use of IHC in diagnostic pathology.