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Malignant pleural mesothelioma (MPM) is the most frequent pleural neoplasm, with asbestos exposure as one of the recognized carcinogen agents, causative in 80% of cases. The prognosis is poor; median survival of untreated cases is 6-9 months, with fewer than 5% of patients surviving 5 years. Sarcomatoid mesothelioma (SM) represents the subtype with the worst outcome and median survival ranging from 3.5 to 8 months. In the last few years, an accurate differentiation between the subtypes of MPM has become a crucial issue, due to differences in chemosensitivity and clinical outcome, and several studies have evaluated different immunohistochemical markers to better define the diagnosis. The different and worse outcome of patients with SM and, in general, nonepithelioid subtypes makes it intriguing to select these cases to better study the biomolecular profile in order to find factors linked to prognosis and/or predictive of therapeutic response. Considering recent studies on miRNA and genetic mapping, further investigation of this rare subtype might represent a field for basic and clinical-translational research providing for more tailored therapies.

In NSCLC, the altered expression of some miRNAs in primary tumor tissues has been correlated with diagnosis and prognosis, while the role of circulating miRNAs as cancer biomarkers is currently emerging. MiRNA expression profile through miRNA Affymetrix array was evaluated on a training set formed by the tumor component (n = 30 NSCLC serum, n = 11/30 tumor tissues) and the control component (n = 10 healthy serum and n = 11/30 noncancerous counterparts). Statistical analyses highlighted the following: a = 55 miRNAs deregulated in tumor serum, b = 27 miRNAs deregulated in tumor tissues, and c = 2 miRNAs deregulated both in tumor serum and in tumor tissues. MiRwalk tool and enrichment pathway analyses selected some miRNAs whose target genes are correlated with the main pathways involved in NSCLC tumorigenesis. The altered expression of the selected miR-486-5p (a), miR-29c* (b), and miR-133a (c) was confirmed in the validation set (n = 40). MiR-486-5p had a higher expression in tumor serum than in tumor tissues (P = 0.004), and miR-29c* showed a lower expression in tumor tissues than in tumor serum (P < 0.001). MiR-133a had a not different expression in both tumor serum and tumor tissues (P = 0.07). The low level of miR-486-5p expression in the serum of affected patients was associated with a worse time to progression of disease (P = 0.010), and serum level of miR-486-5p was a significant prognostic indicator of NSCLC (adjusted hazard ratio = 0.179, P = 0.019). These data suggest the possibility to monitor affected patients through serum and/or tissue samples, analyzing the altered expression of specific miRNAs, in order to detect prognostic biomarkers in the NSCLC.