Cancer research concerning short non-coding RNA sequences and functionally linked to RNA interference (RNAi) have reached explosive breakthrough in the past decade. Molecular technology applies microRNA in extremely wide spectrum from molecular tumor prediction, diagnostics, progression monitoring and prevention. Functional analysis of tissue miRNA and cell-free serum miRNA in posttranscription and translation regulation innovated and restructured the knowledge on the field. This review focuses on molecular epidemiology and primary prevention aspects of the small non-coding RNA sequences.