It is attached to the third, fourth, and fifth ribs and connects with the intercostal muscles between the ribs and with the shoulder joint. In the front, the chest muscles overlay part of the serratus magnus. Near the body's midsection, the breast covers the rectus abdominis, a long flat muscle that extends up the torso from the pubic bone and is attached to the cartilage of the fifth, sixth, and seventh ribs. Such lymph nodes are not grouped in a straight line, like beads on a string. Instead, they are embedded within fat pads - an arrangement that complicates lymph node removal during breast cancer surgery.
Lymph nodes play a major role in the spread of cancer.
These nodes are called Level I nodes. Level II nodes are located just beneath the pectoralis minor muscle. Level III nodes are found above and beyond the pectoralis minor, toward the center of the collarbone. Surface-lying lymphatic vessels usually drain sideways from the breast toward the underarm. Deeper lymphatic vessels pass through the chest muscles, and they eventually drain into the subclavian nodes below the collarbone.