Background: The circular RNAs (circRNAs) are defined as single-stranded RNA
molecules with a length of 100 bp up to 4 kb, resulting from head-to-tail junctions at splice sites
of spliced transcripts. Moreover, they are stable and abundant conserved RNA molecules, which
often have tissue-specific expression and developmental stages. Dysregulation of circRNAs has
been identified in many types of malignancies that mainly affect the progression of human
Methods: This review was prepared via searching of the databases of Science Direct, Directory
of Open Access Journals (DOAJ), Google Scholar, Pub-Med (NLM), Scopus, Web of Science,
and hand searching using relative keywords. The selected papers were fully reviewed and
required information for the review was extracted and summarized.
Results: In recent decades, the prevalence of thyroid cancer, especially papillary thyroid cancer
(PTC), is the most common endocrine cancer increasingly among all cancers, thereby attracting
worldwide attention. The global rate of death from thyroid cancer is approximately 0.2 -0.6 per
100,000 people. Some of the known axes involved in PTC include circ-0025033/miR-1304/miR1231, circPVT1/miR-126, circBACH2/miR-139-5p/LMO4, circ-ITCH/miR-22-3p/CBL/βcatenin, circZFR/miR1261/C8orf4, circRAPGEF5/miR-198/FGFR1, circNUP214/miR145/ZEB2. In this article, we review briefly the most important signaling axes involved in
thyroid cancer. The expression level of microRNA (miRNAs) is regulated by circRNAs.
Conclusion: Thus, circRNAs play an important role in the oncogenic and malignant behavior of
cancer. The fact that circRNAs have been found in abundance in saliva, exosomes and standard
blood samples makes circRNAs a diagnostic marker for diseases, especially cancer screening.