An immunohistochemical study of the presence of c-erbB-2 protein in Paget's disease of the nipple.

Tumours from 45 patients with Paget's disease of the nipple have been stained with antibody 21N which was raised against a peptide from the C-terminus of the predicted c-erbB-2 protein. Positive staining was observed in 41 cases (91%). In 42 cases the underlying mammary carcinoma was also available for study. In all but two cases staining was similar in the Paget's cells and the underlying carcinoma whether the latter was purely in situ ductal (35%) or in situ associated with infiltrating carcinoma (65%); the malignant cells in both components were large and pleomorphic and the in situ ductal carcinoma was of the comedo type. In the two exceptions the underlying carcinoma showed different histological features. The significance of the high levels of c-erbB-2 protein in this pattern of mammary carcinoma is considered.