(a) A schematic diagram of invasion patterns, including amoeboid or mesenchymal single-cell migration, multicellular streaming with or without weak junctional contacts, collective cell migration, tissue folding and expansive growth. Although each pattern can be described as a distinct process, overlapping or converting cell behavior can result in mixed or unstable phenotypes. The intensity range of proposed properties (from absent to strong) is indicated by minus and plus signs. (b) Relationships between leading-edge polarity, cell–cell adhesion, and apicobasal polarity in multicellular migration patterns. The parameters are plotted as a 3D cube to reflect the multiple ways in which transitions between modes of invasion can occur, with the origin in the lower left corner. A determinant not included in the diagram is the stability of cell–substratum interactions, which may also dictate leading-edge polarity and migration mode.^[91]