From a mechanistic point of view, the results obtained to date suggest that high CD99 expression levels may contribute to tumor cell growth and dissemination by interfering with the following: (1) the migration inhibitory activity of KCMF1 [69], a potassium channel modulatory factor reported to affect the biological function of 14-3-3σ protein and stabilize MAPK signaling [70,71], and (2) PI3K/AKT signaling, which is generally repressed, and MAPK signaling, which is stabilized in CD99-deprived cells or after CD99 ligation with specific antibodies [21,56,59]. The gene discussed is CD99; the disease is neoplasm.