[The practice of the genetical diagnosis and its problems]

Carcinoma is a genetic disease. The malignant phenotype is acquired only after several mutations lead to derangement in a variety of gene products. Traditional methods in molecular biology generally work on a "one gene in one experiment" basis, which means that the throughput is very limited and the "whole picture" of gene function is hard to obtain. In recent years, new technology, called DNA microarray, has attracted interest. This technology promises to monitor the whole genome on a single chip so that researchers can have a better picture of the interactions among thousands of genes simultaneously. In cancers, the detection of minimal residual disease may have prognostic and therapeutic implications. Molecular tools are being used more frequently to enhance the detection of minimal residual disease in many types of cancer. Reverse-transcription polymerase chain reaction (RT-PCR) amplification of genes expressed by the tumor in a tissue-specific manner is the method with the highest diagnostic sensitivity. Quantification of tumor mRNA markers expressed by occult circulating tumor cells may be of prognostic value in a variety of neoplasms and disease stages. Medical professionals need to understand the basic concepts and principles of genetics; the role of genetics in diagnosing and managing different cancers; the ethical, legal and social issues surrounding genetic predisposition testing; and how to manage long-term care of patients at high risk for cancer.