Detection of estrogen receptor by immunohistochemistry in pulmonary adenocarcinoma

Background. The distinction between primary adenocarcinoma and metastatic breast carcinoma in the lung is important for therapeutic purposes. There is a good deal of morphologic overlap between primary pulmonary adenocarcinoma and breast carcinoma metastatic in the lung. Many diagnosticians rely upon the presence of estrogen receptor (ER) in tumors of the lung in women in order to make a pathologic diagnosis of metastatic breast carcinoma. There are conflicting data in the literature regarding the presence of ER in lung carcinomas. In this study, we examined primary lung adenocarcinomas with monoclonal antibodies to two different clones to ER (clone 6F11 and clone 1D5), and progesterone receptor by the immunoperoxidase method in order to ascertain if ER is detectable in primary lung adenocarcinomas. Methods. Twenty-five resected solitary pulmonary nonmucinous bronchioalveolar carcinomas (15 female, 10 male) and 20 resected solitary pulmonary adenocarcinomas of no special type (12F, 8 mol/L) were studied by the immunohistochemical method using heat-induced epitope retrieval. Immunostaining was semiquantitated, and positive results included nuclear staining for ER and progesterone receptor. All of these tumors were documented as primary pulmonary adenocarcinomas clinically and pathologically. Results. Nuclear ER was seen only with the 6F11 clone, in 56% of the bronchioalveolar type and 80% of the no special type. No nuclear ER was seen in carcinomas utilizing the 1D5 clone. There was no progesterone receptor detectable in carcinomas. Conclusions. Estrogen receptor is present in the majority of lung adenocarcinomas, and detection of ER in lung adenocarcinomas is dependent upon the antibody clone that is used. Epitope recognition may account for the differences in immunoreactivity between these two antibodies, although a cross-reactive antibody reaction cannot be completely excluded. Further study is warranted to discern the nature of the 6F11 clone immunoreactivity with nuclei of lung adenocarcinomas. The clinical significance and ramifications of ER in pulmonary adenocarcinomas remain unknown. Caution should be exercised by clinicians and pathologists in accepting a diagnosis of metastatic breast carcinoma in lung based on the presence of ER detected by clone 6F11. (C) 2002 by The Society of Thoracic Surgeons.