IntroductionEarly diagnosis provides the best hope many have of beating cancer. Unfortunately, this is not the end of the fight for many cancer patients. Primary tumors can be successfully treated early, only to later be found to have metastasized to other areas of the body. The common medical definition of metastasis is: the spread of cancer from one part of the body to another. Tumors formed from cells that have spread are called “secondary tumors” and contain cells similar to those of the original (primary) tumor. This definition may be the reason why early treatment of a primary tumor is ineffective against metastatic tumor cells. As the definition suggests, the accepted model for tumor cell metastasis is through clonal evolution, where secondary tumors have similar genomes to the primary tumor. Recent studies suggest, however, that this may not be accurate. In recent studies, a significant divergence between primary and secondary tumors in renal cell metastases and breast metastases was discovered. An alternative model, of parallel evolution, would explain why therapies aimed at primary tumors are not successful against metastatic cells. Further research into this alternative model could lead to therapies that target not only the properties of the primary tumor but also those of the secondary tumor. tumor and save many from the burden of fighting cancer again. Methods This study took 386 breast cancer patients and divided them into two groups. M0, patients showing cells without metastasis, and M1 patients, those who showed metastasis and performed a genomic analysis, or comparative genomic hybridization (CGH) of cytokeratin... middle of paper... tumor cells that could potentially spread, mutate, change and grow into another tumor. More emphasis needs to be placed on the development of disseminated cells because changes in their growth cannot be reflected by genomic data obtained from primary tumor data; consequently, they cannot be addressed in the same way. The main idea of ​​this study is to underline: "the need to validate potential cellular targets for adjuvant and systemic therapies directly on disseminated tumor cells" (Cancer Cell: July 2003). The article under discussion is: Gray, JW, Emerging evidence for early metastasis and the parallel evolution of primary and metastatic tumors. Cancer Cell July 2003. Schmidt-Kittler, O. et al., From latent disseminated cells to overt metastasis: genetic analysis of systemic progression of breast cancer. PNAS 100, 7734 (2003).