The blood supply of the breast is critically important when trying to understand breast cancer and how it spreads. As a general rule anywhere in the body, cancer may spread by one of three means. In the case of the breast, the most common method of cancer spread is via the lymphatics and by direct invasion, but haematogenous spread also occurs. Another general rule in the body is that lymph vessels draining an organ, run alongside the arteries that supply blood to that organ. These are therefore the most common sites for lymph node metastases in breast cancer and are important when the stage and prognosis of the disease are being determined.
Blood draining from the breast does so via the veins that run with the arteries mentioned above.
This is particularly important in the case of the intercostal veins since these connect with the azygos veins deep within the chest, and so allow a means of spread to the spinal column - a site where breast cancer often spreads. The breast develops rapidly at puberty in response to circulating hormones produced in the ovary - especially oestrogen. The monthly menstrual cycle causes the breast glandularity to increase. In summary, the breast is a complex anatomical and functional organ. It can be affected by a number of both benign and cancerous conditions.