How long does breast cancer take to spread if it goes untreated? are we talking months or years? or 10 years +

No set time: My rule of thumb: treatment should be initiated = 6 weeks unless it's a particularly fulminant lesion-in which case psychological burden of delay alone dictates more immediate action. The fear of cancer => stress which is immunosuppressive. Do not make a final decision until you have consulted with all of these 4 specialists: oncology, general surgery, plastic surgery and radiation oncology.