Computational tools with a balanced sensitivity and specificity in identification of candidate cancer drivers are highly desired. In this study, we propose a new statistical test, namely the d_J/d_S ratio test, to compute the relative mutation rate of exon/intron junction sites (d_J) to synonymous sites (d_S); observation of d_J/d_S ratio larger than 1 in cancer indicates positive selection for splicing deregulation, a signature of cancer driver genes. Using this method, we analyzed the data from The Cancer Genome Atlas and identified hundreds of novel putative cancer drivers. Interestingly, these genes are highly enriched in biological processes related to the development and maintenance of multicellularity, paralleling a previous finding that cancer evolves back to be unicellular by knocking down the multicellularity-associated genetic network.