Mother diagnosed with stage 4 breast cancer in breast, multiple lymph nodes, liver and bones. how long does she have?

Depends: First, it is now clear we physicians can't predict the survival of any single individual very precisely. We can say that of a thousand patients with a given condition, half will still be alive at x date. For a breast cancer patient, even one with stage IV disease, the prognosis depends on many things: is the tumor hormone sensitive or not? Is there a her2-neu gene amplification? So it depends.