Malignant and benign papillary lesions of the breast.

This presentation describes criteria that we found most helpful in classifying the various proliferative changes of the breast and in separating papillary carcinoma from other benign papillary lesions. The criteria we used are easily understood and extremely reproducible. The true incidence of benign proliferative changes in fibrocystic disease and the significance of these lesions in later development of cancer were determined by studying 200 randomly selected cases of fibrocystic disease seen at least 10 years earlier. Of the 200 cases of fibrocystic disease, 40 showed intraductal papillomatosis or terminal duct hyperplasia. None of the patients with benign proliferative lesions for whom we have complete follow-up data (up to 14 years) developed cancer. In order to determine the type of proliferating cells in papillary carcinoma and benign proliferative lesions, some of the recently encountered cases were studied by transmission and scanning electron microscopy and histochemistry. Our ultrastructural and histochemical study suggests that both epithelial and myoepithelial cells participate in papillary lesions of the breast.