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

Abstract

To determine the frequency of Her-2 overexpression in patients with poorly differentiated carcinoma or poorly differentiated adenocarcinoma of unknown primary site. Tumor specimens from 100 patients with poorly differentiated carcinoma or poorly differentiated adenocarcinoma were stained for the Her-2 protein using the Dako immunohistochemical method. Clinical and pathologic characteristics of patients with and without Her-2 overexpression were compared. Staining for Her-2 overexpression was successful in 94 of 100 patients. Ten (11%) of 94 tumor specimens overexpressed Her-2. Eight of 10 overexpressors had poorly differentiated adenocarcinoma, and all overexpressors had predominant tumor location above the diaphragm, usually in the mediastinum or lungs. Her-2 overexpression occurs in a minority of patients with poorly differentiated carcinoma/adenocarcinoma of unknown primary site. Because most overexpressors had poorly differentiated adenocarcinoma, further evaluation of patients with adenocarcinoma of unknown primary site is necessary to determine the frequency of Her-2 overexpression in this common subgroup. Evaluation of the efficacy of trastuzumab in Her-2 overexpressors with carcinoma of unknown primary site is indicated.