MicroRNAs (miRNAs) correspond to a class of non-coding RNAs of 17-25 nucleotides. Identified decades ago, their primary role is to regulate the transcription, translation and degradation of mRNA, thereby regulating gene expression. Moreover, miRNAs exert epigenetic effects on DNA methylation and histone modification. They also play a role in intercellular signaling and participate as regulators in some physiological and developmental processes. Interestingly, they regulate hormonal production and activity since they target genes encoding for hormones or enzymes involved in their production or metabolism, influencing hormonal concentration. On the other hand, miRNAs play a role in apoptosis and carcinogenesis. They control oncogenes and tumor suppressor genes through tumor suppressor miRNAs and oncomiRs. Furthermore, miRNAs are involved in different signaling pathways related to carcinogenesis.

While most miRNAs are found inside the cell, some are extracellular and can be detected in different body fluids. Whether circulating, encapsulated in exosomes, or bound to specific proteins (Ago2, NPM 1) they are proposed as markers in cancer because, unlike RNA, miRNAs are exceptionally stable against environmental conditions and even in fixed tissues. The gold-standard for miRNA quantification is quantitative reverse transcriptase PCR (RT-qPCR). Other methods such as: Northern blotting, in situ hybridization, real-time PCR, miRNA microarray and next-generation sequencing (NGS) have also been used.

In the context of endocrine neoplasias, it has been described that some miRNAs are abnormally expressed in the serum or tissue of patients with ovarian carcinomas and also in papillary thyroid cancer (PTC). In PTC, miRNAs can be either up-regulated or down-regulated and specific patterns correlate with clinicopathological factors such as tumor size, invasiveness, progression and aggressiveness. Regarding adrenal neoplasms, some increased miRNAs have been found in the plasma of patients with adrenal adenomas or carcinoma. Specific miRNAs exhibit higher or lower levels of expression in carcinomas compared to adenomas or normal adrenals. Their evaluation could allow differentiation between benign and malignant tumors using a non-invasive method. Moreover, certain miRNAs have been associated with secretory tumors.

In this article collection, we welcome Original Research, Reviews, Mini-Reviews, Opinion and Perspective articles on the role of miRNAs in the diagnosis of endocrine cancer. In particular, we are interested in collecting manuscripts related to, but not limited to, the following themes:

- miRNA as oncogenes and tumor suppressors in the endocrine system

- Regulation of genesis, development and spread of endocrine neoplasias through miRNA expression.

- The value of miRNAs as potential biomarkers in diagnosis, prognosis and therapy in endocrine neoplasias: pituitary, thyroid, parathyroid, adrenal, ovary, etc.

- Implications of miRNA in multiple endocrine neoplasia syndromes

- Pharmacological/therapeutic approaches to treat endocrine cancer by targeting miRNAs

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MicroRNAs in the diagnosis of endocrine neoplasias and cancers