Circular RNAs (circRNAs) are a large type of noncoding RNAs characterized by 
their circular shape resulting from covalently closed continuous loops. They are 
known to regulate gene expression in mammals. These tissue-specific transcripts 
are largely generated from exonic or intronic sequences of their host genes. 
Although several models of circRNA biogenesis have been proposed, the 
understanding of their origin is far from complete. Unlike other noncoding RNAs, 
circRNAs are widely expressed, highly conserved and stable in cytoplasm, which 
confer special functionalities to them. They are known to serve as microRNA 
(miRNA) sponges, regulators of alternative splicing, transcription factors and 
encode for proteins. The expression of circRNAs is associated with several 
pathological states and may potentially serve as novel diagnostic or predictive 
biomarkers. CircRNAs are known to regulate the expression of numerous 
cancer-related miRNAs. The circRNA-miRNA-mRNA axis is a known regulatory pattern 
of several cancer-associated pathways, with both agonist and antagonist effects 
on carcinogenesis. In consideration of their potential clinical relevance, 
circRNAs are at the center of ongoing research initiatives on cancer prevention 
and treatment. In this review, we discuss the current understanding of circRNAs 
and the prospects for their potential clinical application in the management of 
cancer patients.