Overexpression of Her-2 in patients with poorly differentiated carcinoma or poorly differentiated adenocarcinoma of unknown primary site

Purpose: To determine the frequency of Her-2 overexpression in patients wit h poorly differentiated carcinoma or poorly differentiated adenocarcinoma o f unknown primary site. Patients and Methods: Tumor specimens from 100 patients with poorly differe ntiated carcinoma or poorly differentiated adenocarcinoma were stained for the Her-2 protein using the Dako immunohistochemical method. Clinical and p athologic characteristics of patients with and without Her-2 overexpression were compared. Results: Staining for Her-5 overexpression was successful in 94 of 100 pati ents. Ten (11%) of 94 tumor specimens overexpressed Her-2. Eight of 10 over expressors had poorly differentiated adenocarcinoma, and all overexpressors had predominant tumor location above the diaphragm, usually in the mediast inum or lungs. Conclusion: Her-5 overexpression occurs in a minority of patients with poor ly differentiated carcinoma/ adenocarcinoma of unknown primary site. Becaus e most overexpressors had poorly differentiated adenocarcinoma, further eva luation of patients with adenocarcinoma of unknown primary site is necessar y to determine the frequency of Her-5 overexpression in this common subgrou p. Evaluation of the efficacy of trastuzumab in Her-2 overexpressors with c arcinoma of unknown primary site is indicated. J Clin Oncol 18:632-635. (C) 2000 by American Society of Clinical Oncology.