[Clinical value of gene diagnosis in breast cancer].

Gene diagnosis has been mainly performed for three purposes, 1) to assess the prophylactic risk from genetic alterations of candidate gene, 2) to confirm the diagnosis from a small volume of cancer cells using polymerase chain reaction method and 3) to understand the biological characteristic of the tumor by assessing genetic instabilities. BRCA1 and BRCA2 are quite important candidate genes in familial breast cancer. Recently, prophylactic mastectomy has been performed for BRCA1/2 carriers in Western countries. Telomerase activity can be a sensitive and definitive analysis for diagnosing certain cancers, and the reverse transcripted polymerase chain reaction (RT-PCR) method can detect a small number of metastatic cancer cells in the axillary lymph node. Furthermore, genetic abnormalities, such as abnormalities in oncogenes or/and tumor suppressor genes and loss of heterozygosity or microsatellite instability, facilitate understanding of the biological characteristics of these tumors. It is necessary for the clinician to understand the significance and usefulness of gene diagnosis.