The higher number of surface nodes and larger size of lung metastasis observed in MMTV-PyMT SK1-/- compared to MMTV-PyMT SK1+/+ mice suggests that the effect of SK1 downregulation in breast cancer cell migration, and processes such as angio- and lymph-angiogenesis, are possibly exceeded by other processes regulating breast cancer metastasis in the MMTV-PyMT model analyzed. The gene discussed is SPHK1; the disease is breast cancer.