Their involvement in carcinogenesis represents an important area of investigation for the development of their clinical applications: diagnostics, monitoring and therapeutics. MicroRNA profiles can distinguish between normal and cancerous tissue, identify tissue of origin and also discriminate different subtypes or specific oncogenic abnormalities. Indeed, microRNA mis-expression patterns are more accurate in identifying the origin of tumours that are otherwise difficult to be determined, suggesting that tumours more clearly maintain a unique tissue microRNA expression profile.