Although we find no evidence of rhodopsin in breast cancer cells to act as a light sensor, we do find high epression of CRY2 in these cells, and CRY2 can also act as a light sensor, absorbing light in its associated FAD molecule, intriguingly also specifically in the blue wavelength region of 450–480 nm (Hoang, et al. 2008), which may contribute to the activation of PDE6 in these cells, and the alteration in cGMP levels, leading to dysregulation of circadian genes, alterations in circadian rythyms, and the inducement or perpetuation of the growth of breast cancer cells. The gene discussed is CRY2; the disease is breast carcinoma.