I'm 68 i have visible blue veins in my left breast, nothing in my right. had mammogram 4 mos ago and breast exam by doc 3 mos . are veins sign of bc?

Unlikely: Breast cancer will rarely cause venous problem like you have. It is more related to circulation. Have your primary care doctor monitor the veins for any further enlargement or any new veins showing up which may justify checking your circulation(veins and arteries in the chest wall and in the left arm region. Nothing immediately worrisome.

Normal finding: I am amazed about how often I have women ask me about the veins on their breast. Occasionally they are spider veins but mostly they are blue veins. These are almost always normal findings and normal variations of chest veins. They tend to be more pronounced in fair skinned females and they may be related to hereditary factors or even pregnancies. No treatment is necessary unless for cosmetics.

No,: as an isolated finding, visible veins are not associated with breast cancer. Is there associated pain or swelling? If you are concerned about it, have your doctor take a look.