[Genome Abnormality and Histological Findings in Breast Carcinoma]

Breast cancers contain variable histologies as well as biology. Gene expression profiling and cluster analyses have been performed since the beginning of the 21st century. The use of intrinsic subtype classification has replaced histological classification of breast carcinomas, as it frequently yields the same results. For examples, around 80% of triple negative (estrogen receptor-, progesterone receptor-, and HER2-negative) cancers are of the basal-like subtype. In daily practice, adjuvant therapy is selected based on histological features, but the results of ordinal cluster analyses and histological intrinsic subtypes are not always the same for individual cases. With advanced genetic analysis, new concepts have been elucidated, ie, the molecular identification of claudin-low breast cancer. Proposals of a new classification system and a new therapeutic approach are expected in the future.