The interplay between tumor cells and their microenvironment plays a pivotal 
role in tumor development and progression. Although a growing body of evidence 
has established the importance of the tumor microenvironment, an understanding 
of the crosstalk between its components and cancer cells remains elusive. The 
pathways triggered by microenvironmental factors could modulate cancer-related 
gene transcription, also affecting small noncoding RNAs, microRNAs, which have 
emerged as key posttranscriptional regulators of gene expression, directly 
involved in human cancers. Although microRNAs regulate most biological 
mechanisms, their role in the tumor microenvironment has only recently become 
the focus of intense research. In this paper, we focus on the intertwined 
connection between the tumor microenvironment and aberrant expression of 
microRNAs involved in carcinogenesis. We also discuss the emerging roles of 
microRNAs in the tumor microenvironment as it relates to cancer progression. We 
conclude that microRNAs are critical for our understanding of the development of 
cancer, and that targeting microRNA signaling pathways in the microenvironment 
as well as in tumor cells opens new therapeutic avenues to the global control of 
cancer.