Estrogen receptor gene (ESR1) amplification occurs rarely in ovarian cancers

Abstract

Amplification of the gene encoding estrogen receptor alpha occurs in about 20% of breast cancers and is an important mechanism for estrogen receptor overexpression in this tumor type. In ovarian cancer, overexpression of estrogen receptor protein has been described in more than two thirds of cases. To study a potential role of estrogen receptor alpha gene amplification for estrogen receptor overexpression in ovarian cancer, a tumor tissue microarray containing 428 ovarian caners was analyzed by fluorescence in-situ hybridization for estrogen receptor alpha gene amplification and immunohistochemistry for estrogen receptors expression. The estrogen receptor alpha gene status was successfully determined in 243/428 arrayed cancers. Estrogen receptor gene amplification was found in 5/243 (2%) of tumors. Amplification levels were usually low with 4-8 estrogen receptor alpha gene copies. However, one case had a high level amplification with more than 30 estrogen receptor alpha gene copies. All 5 amplified tumors were estrogen receptors positive with 3/5 tumors showing highest (Allred score 7-8) estrogen receptor levels. The data demonstrate that estrogen receptor alpha amplification occurs only rarely in ovarian cancer.