Movement of human mammary tumour cells in culture: exclusion of fibroblasts by epithelial territories.

Time-lapse cinematography was used to investigate the movement of confronting populations of human mammary epithelium and stromal cells (fibroblasts). Epithelial cell islands from fibroadenomas and from normal lacteal secretions completely excluded the fibroblasts, and individual cell territories were maintained even in dense cultures. Electron microscopy of the boundary between epithelium and fibroblasts showed that the two cell types made contact. In contrast, epithelial islands from two carcinomas did not retain territorial integrity and allowed penetration of mammary fibroblasts. Confronting homologous eptihelial islands from benign tumours merged, but this was shown to be due to interdigitation rather than free mixing of cell. Epithelial cells moved actively but unlike fibroblasts they retained their neighbour relationships.