During the last two decays the tremendous success in molecular biology and genetics which has surprised the entire world. So that today the sequencing of whole genome has been possible for each human individual to estimate its being affected with cardiovascular and cancer diseases. However, these achievements have some important limitations and deep ethical issues which might be ignored. Genetic diagnosis of cancer shows that how we should look at our predictions. In this article, some of the unseen truth regarding genetic tests for breast cancer is discussed. This could be extended to other genetic diseases and cancer.