Genome-wide expression profiling studies reveal a transcriptionally distinct sub-type of human solid tumors with a marked propensity toward metastatic dissemination, highly malignant clinical behavior, and poor therapy outcome in cancer patients diagnosed with the early stage carcinomas of various origins. This sub-set of tumors acquires full metastatic potential, including an emergence and seeding of potent metastasis precursor cells, early in tumor progression. Collectively, these data suggest an early involvement in development of this transcriptionally defined sub-type of human carcinomas of a highly malignant combination of mutant alleles conferring the proclivity to metastasize and/or an engagement in transformation and tumor progression of stem cells and/or early progenitor cells. Enrichment of primary tumors with normal stem cells increases the likelihood of horizontal genomic transfer (large-scale transfer of DNA and chromatin) between stem cells and cancer cells via cell fusion and/or uptake of apoptotic bodies and generation of reprogrammed somatic cell hybrids with self-renewing highly malignant phenotype.