Breast lymphatic system. Artwork showing the internal structure of a human breast and its lymphatic system. Lymph nodes (purple) are joined by a network of lymph vessels.  Breast tissue (yellow) surrounds the nipple and lies on top of the ribs. Other bones and muscles are also seen. The left arm is raised to show the axillary lymph nodes of the armpit. If these lymph nodes are hard and lumpy, this can indicate the presence of a cancer in the breast that has spread to the armpit. Regular checks of the armpit can aid an early diagnosis of breast cancer.