Radical mastectomy involves removing all the breast tissue, overlying skin, the pectoralis muscles, and all the axillary lymph nodes. Skin was removed because the disease involved the skin, which was often ulcerated. The pectoralis muscles were removed not only because the chest wall was involved, but also because it was thought that removal of the transpectoral lymphatic pathways were necessary. It was also thought, at that time, that it was anatomically impossible to do a complete axillary dissection without removing the pectoralis muscle.