Long-Term Expiant Culture of Normal Mammary Epithelium1

Mammary epithelium and surrounding stroma have been maintained in an expiant system for 1 to 6 months and subse quently xenografted into athymic nude mice. The morphologi cal characteristics of 26 cases of normal human mammary epithelium in long-term expiant culture were described, using high-resolution light and electron microscopy. Normal human breast tissue specimens were obtained from immediate autopsy or surgical resection. The expiants were cultured in Connaught Medical Research Laboratories Medium 1066 supplemented with serum, insulin, and hydrocortisone. The histotypic features of the mammary epithelium in both the central portion of the expiant and the epithelial outgrowth onto the surface of the expiant were described. In some cultures, the cells acquired more keratin and formed multicellular blister-like domes. Tis sues from eight cases after 1 to 14 weeks in culture were xenografted in athymic nude mice and were maintained up to 924 days.