Cancer, a local disease at an early stage, systemically evolves as it progresses by triggering alterations in surrounding microenvironment, disturbing immune surveillance and further disseminating its molecular contents into circulation. This pathogenic characteristic of
cancer makes the use of biofluids such as blood/serum/plasma, urine, tear and cerebrospinal fluids credible surrogates harboring
tumor tissue-derived molecular alterations for the detection of
cancer. Most importantly, a number of recent reports have credentialed the clinical validity of saliva for the detection of systemic diseases including
cancers. In this review, we discussed the validity of saliva as credible biofluid and clinical sample type for the detection of
cancers. We have presented the molecular constituents of saliva that could mirror the systemic status of our body and recent findings of salivaomics associated with
cancers. Recently, liquid biopsy to detect
cancer-derived
circulating tumor DNA has emerged as a credible
cancer-detection tool with potential benefits in screening, diagnosis and also risk management of
cancers. We have further presented the clinical validity of saliva for liquid biopsy of
cancers and a new technology platform based on electrochemical detection of
cancer-derived ctDNA in saliva with superior sensitivity and point-of-care potential. The clinical utilities of saliva for the detection of
cancers have been evidenced, but
biological underpinning on the existence of molecular signatures of
cancer-origin in saliva, such as via exosomal distribution, should be addressed in detail.