Search

Distributions of actin and type IV collagen were investigated immunohistochemically as markers for myoepithelial cells and basement membranes. Carnoy's and Methacarn-fixed, paraffin-embedded tissues from 103 human breast lesions from 103 patients were examined; 65 with carcinomas, 27 with mastopathies, 9 with fibroadenomas and 2 with phyllodes tumours. Fifty-five samples of the normal mammary gland tissue adjacent to tumours were also included for comparison. In normal breast and benign breast diseases, type IV collagen was identified around the mammary glandular cells and actin-positive cells were demonstrated to attach to basement membranes. In noninvasive carcinomas, type IV collagen was found as a continuous lining around a cell nest, while actin-positive cells were usually absent in ductal but quite numerous in lobular carcinomas. In invasive carcinomas, type IV collagen was fragmented or absent and actin-positive cells were very uncommon around the fragmentary basement membranes. These results suggest that the different distributions of myoepithelial cells and basement membrane material is useful in the differential diagnosis of surgical pathology of the breast.

Mammary tumours were induced by the direct dusting of 1 mg, 7,12-dimethylbenz(a)anthracene (DMBA) powder onto the mammary gland of both 30-day-old female and male Sprague-Dawley rats, and the tumours were examined histologically. Mammary tumours developed in 43/43 (100%) of the females 11 to 20 weeks after DMBA dusting and 16/23 (70%) of the males 18 to 28 weeks after dusting, while non-mammary spindle cell sarcomas occurred in 5/23 (22%) of the males 15 to 24 weeks after dusting. A variety of benign and malignant mammary tumours of epithelial and/or mesenchymal origin were induced, which are comparable to human mammary tumours. Different histological patterns were observed in different areas of the same tumours. Ovariectomy revealed hormone (ovary)-dependency in 10/17 (59%) of the tumours, revealing regressing epithelial and proliferating mesenchymal tumour elements on histological examination.