I do not know the exact number of breast cancer patients undergoing surgery using blue dye. I do know over 200,000 new cases of breast cancer are diagnosed every year in the US. In addition some patients after first surgery get a recurrence and are subject to repeat surgeries. I would assume the no.is north of 200,000. This is just the US, Europe should have a similar no. of cases. This does not include melanoma which is a fairly common cancer.