The association of CD44 with the most aggressive subtype of disease is consistent with the well-established cellular functions of CD44 in promoting cell invasion and cell adhesion in vitro, and the capacity for CD44 to increase spontaneous metastasis of breast cancer cells in vivo [7,8; McFarlane S, Coulter J, Waugh DJJ, unpublished observations]. The gene discussed is CD44; the disease is breast cancer.