Expression of minichromosome maintenance proteins in the exfoliated cells supplement sputum cytology in the diagnosis of lung cancer.

Abstract

Objective: Sputum cytology is recognized as a straightforward and noninvasive way to diagnose lung cancer, although its clinical utility has not yet been investigated. The objective of the study was to detect and classify cancerous cells in sputum by examining their expression of minichromosome maintenance proteins (MCM2 and MCM7). In addition, the study attempted to evaluate these proteins' potential as biomarkers of lung cancer lesions and their relationships with clinicopathological characteristics.

Material and methods: MCM2 and MCM7 expression in sputum samples was evaluated using immunocytochemistry in sputum cell blocks (n = 97), and their correlation with clinicopathological features was examined. Diagnostic performance was evaluated as a function of sensitivity and specificity.

Results: Immunoexpression of MCM2 and MCM7 was confined to the nuclei of malignant cells alone, suggesting its potential as a differential diagnostic marker. They showed significant correlations with tumor cytology (P < 0.001), while MCM7 alone exhibited a significant correlation with tumor stage (P = 0.014). The overexpression of these markers was notably pronounced in lung adenocarcinoma compared to other subtypes. In terms of characterizing malignant cells, MCM7 protein demonstrated the highest sensitivity at 92% with an area under the curve (AUC) of 0.961, whereas MCM2 had a sensitivity of 80% and AUC of 0.901.

Conclusion: This study presents the inaugural use of MCM7 immunocytochemistry on exfoliated cells in sputum samples, proposing that analyzing immunocytochemical markers in sputum could serve as a cost-effective approach for diagnosing lung cancer. Integrating these assessed markers into routine cytopathology laboratories could augment traditional morphological evaluations, thereby improving the sensitivity of sputum cytology.