The body has about 20 to 40 bean-shaped axillary lymph nodes located in the underarm area. These lymph nodes are responsible for draining lymph – a clear or white fluid made up of white blood cells – from the breasts and surrounding areas, including the neck, the upper arms, and the underarm area. They are about 1cm in size and are arranged into five groups: subscapular axillary (posterior), apical (medial or subclavicular), pectoral axillary (anterior), brachial (lateral), and central lymph nodes. The subscapular axillary lymph nodes are located on the lower part of the armpit’s posterior (rear) wall. The apical and pectoral nodes are located respectively on the upper and lower parts of the pectoralis minor, a thin, flat muscle of the chest. The brachial nodes are located relative to the axillary vein's medial (near the middle) and posterior portions. The central axillary lymph nodes are located inside the adipose tissue near the armpit’s base. Breast cancer initially develops as a lump in the breast, but often spreads to the axillary lymph nodes, which allows it to access the lymphatic system and travel to other areas of the body. During surgical procedures to remove breast cancer, including lumpectomies and partial, modified radical, radical, or total mastectomies, surgeons often remove some of the axillary lymph nodes to determine whether the breast cancer has spread, and also to determine cancer staging.