Objective: To compare the relationship between Her-2/neu in the invasive and in situ components of carcinoma.
Study design: Using immunohistochemistry, this study compares the Her-2/neu status in the in situ and invasive components of 200 cases of ductal carcinoma of the breast. A 0-3+ grading scale was used to semiquantitate Her-2/neu protein expression.
Results: Twenty-five cases (12.5%) demonstrated a difference of 2 or more grades between the in situ and invasive components. The in situ component always showed higher expression of Her-2/neu than did the invasive component when protein expression was discordant. Comedo carcinoma was the in situ component in 12 of the 25 discordances in Her-2/neu expression.
Conclusion: Significant heterogeneity exists between Her-2/neu expression in the in situ component and invasive components of adenocarcinoma of the breast. When discordance exists, the in situ component shows higher levels of expression.