The breast also has connective tissue, arteries, veins, nerves, lymph nodes and lymph vessels. The lymph vessels and the veins may be associated with the spread of breast cancer.

Most of the smaller veins of the breast drain into the internal mammary vein, which is the main vein taking blood from the breast. Some others drain into veins that run under the arm, or along the ribs. It’s possible for cancer to spread from the breast to the lungs and other organs through the blood stream.