SLITs and ROBOs have been implicated in development of both the normal mammary gland and breast cancer (Marlow et al., 2010; Macias et al., 2011; Harburg et al., 2014; Ballard Mimmi et al., 2015; Zhao et al., 2016) and ROBO1 signaling has been shown to mediate differentiation for milk secretion (Cazares et al., 2021). The gene discussed is ROBO1; the disease is breast cancer.