Scientists have identified four biomarkers that may help resolve the difficult differential diagnosis between malignant pleural mesothelioma (MPM) and noncancerous pleural tissue with reactive mesothelial proliferations (RMPs).
This is a frequent differential diagnostic problem in pleural biopsy samples taken from patients with clinical suspicion of MPM. The ability to make more accurate diagnoses earlier may facilitate improved patient outcomes.
“Our goal was to identify microRNAs (miRNAs) that can aid in the differential diagnosis of MPM from RMPs,” said lead investigator Eric Santoni-Rugiu, MD, PhD, of the Laboratory of Molecular Pathology at the Department of Pathology of Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. The small, noncoding RNA strands known as miRNAs are composed of approximately 22 nucleotides, and they have been shown to be potential diagnostic, prognostic, and predictive markers in other cancers.
After screening 742 miRNAs, the investigators identified miR-126, miR-143, miR-145, and miR-652 as the best candidates to diagnose MPM. Using results from these four miRNAs, tissue samples from patients with known outcomes could be classified as MPM or noncancerous with an accuracy of 0.94, sensitivity of 0.95, and specificity of 0.93. Further, an association between miRNA levels and patient survival could be made.
“The International Mesothelioma Interest Group (IMIG) recommends that a diagnostic marker of MPM have sensitivity/specificity of >0.80, and these criteria are fulfilled by our miRNA classifier,” commented Santoni-Rugiu. The authors suggest that diagnostic accuracy can be further improved by adding immunohistochemical testing of miRNA targets in biopsy tissue to their miRNA assay. This combined assay could enable analysis of samples with low tumor cell count. Their study appeared in the Journal of Molecular Diagnostics (2014; doi:10.1016/j.jmoldx.2014.03.002).
MPM, which is linked to long-term asbestos exposure, is an aggressive cancer originating from the mesothelial cells that line the membrane surrounding each lung, known as the pleura. Distinguishing MPM from noncancerous abnormalities, such as reactive mesothelial hyperplasia or fibrous pleurisy (organizing pleuritis), can be challenging as there are no generally accepted diagnostic biomarkers for differentiating these two conditions. As a result, patients often present with the disease when they are already at an advanced stage, and less than 20% of patients can be successfully treated surgically.
The current study, however, suggests that miRNAs may provide new opportunities for improving the accuracy of the differential diagnosis between MPM and noncancerous pleural conditions. If further validated, the combination of ISH for miRNAs with immunohistocemical testing of miRNA targets may therefore have the potential to aid in the diagnosis, and thus outcome, of MPM.