The article reviews the role of microRNAs (miRNAs) in body fluids as biomarkers for cancer detection, diagnosis, and treatment response. MiRNAs, small noncoding RNAs, play a crucial role in gene expression regulation and are implicated in various diseases, including cancer. The presence of miRNAs in serum, plasma, and other body fluids suggests their potential as noninvasive biomarkers. The deregulation of miRNA expression is an early event in tumorigenesis, making it useful for early cancer detection. The review discusses the potential of miRNAs as reliable biomarkers and treatment-response predictors, as well as their potential as new patient selection criteria for clinical trials. It also explores the concept that miRNAs can function as hormones through their secretion in plasma and their delivery to distant sites in the body. The article highlights the stability and activity of miRNAs in body fluids, emphasizing the need for standardized methods for detection and validation. Finally, it concludes by discussing the broader implications of miRNAs as biomarkers for various human conditions and diseases.The article reviews the role of microRNAs (miRNAs) in body fluids as biomarkers for cancer detection, diagnosis, and treatment response. MiRNAs, small noncoding RNAs, play a crucial role in gene expression regulation and are implicated in various diseases, including cancer. The presence of miRNAs in serum, plasma, and other body fluids suggests their potential as noninvasive biomarkers. The deregulation of miRNA expression is an early event in tumorigenesis, making it useful for early cancer detection. The review discusses the potential of miRNAs as reliable biomarkers and treatment-response predictors, as well as their potential as new patient selection criteria for clinical trials. It also explores the concept that miRNAs can function as hormones through their secretion in plasma and their delivery to distant sites in the body. The article highlights the stability and activity of miRNAs in body fluids, emphasizing the need for standardized methods for detection and validation. Finally, it concludes by discussing the broader implications of miRNAs as biomarkers for various human conditions and diseases.