Motility in the tumor microenvironment. Intravital imaging (IVI) using multiphoton microscopy of primary mammary tumors from transgenic Neu deletion mutant (activated receptor) (Neu-NDL), Neu-YD and Neu-YB cyan fluorescent protein mice. Thirty-minute time-lapse Z-series were collected, and the average total cell motility was quantified per 50-μm Z-stack (five sections imaged at 10-μm intervals). Data are means and SEM of 27 to 32 separate Z-stacks. *P < 0.05, **P < 0.005 by Mann-Whitney U test; n = 13 Neu-NDL mice, n = 8 Neu-YD mice and n = 12 Neu-YB mice.