The BT-549 line was isolated in 1978 by W.G. Coutinho and E.Y. Lasfargues. Source tissue consisted of a papillary, invasive ductal tumor which had metastasized to 3 of 7 regional lymph nodes. The established population was polymorphic with epithelial like components and multinucleated giant cells. A mucin-like material was secreted into the medium.