The status of cyclooxygenase-2 expression in ductal carcinoma in situ lesions and invasive breast cancer correlates to cyclooxygenase-2 expression in normal breast tissue

OBJECTIVES: There is a paucity of data on cyclooxygenase (COX)-2 expression in normal breast tissue and on the changes in COX-2 expression from normal tissue via ductal carcinoma in situ (DCIS) lesions to invasive cancer. The aim of this study, therefore, was to investigate COX-2 protein expression in normal breast tissue, DCIS, and invasive breast cancer in samples from the same patients. METHODS: In 39 patients, we investigated and compared COX-2 expression in paired samples of invasive cancer and normal adjacent breast epithelium by immunohistochemistry with a monoclonal COX-2 antibody. Furthermore, in 29 of these cases, we also analyzed a concomitant DCIS lesion. RESULTS: Patients without COX-2 expression in normal breast tissue also do not express COX-2 in invasive breast cancer and in DCIS lesions, respectively. Conversely, COX-2 expression in normal breast tissue was an indicator for COX-2 expression in the paired breast tumors. There was no significant correlation between COX-2 expression and pathologic tumor stage, nodal status, hormone receptor status, tumor size, grading, and lymphovascular space involvement. CONCLUSIONS: This is the largest study to date investigating COX-2 in paired samples of breast tumors and normal adjacent breast tissue. Our data are consistent with the hypothesis that COX-2 overexpression is an early event in breast carcinogenesis.