CYP19A1 and neoplasm: In conclusion ERS1, alone or in combination with ERS2 or CYP19A1, is the most determining prognostic factor within the analyzed 3 genes taking into account its deregulation in tumor tissues, its relationship with survival, and that the hazard ratio when it is combined with other variables is higher than that for ERS2. The origin of the deregulation, which appears to be causing underexpression of ERS1 RNA has yet to be elucidated.