In the later stages, skin breakdown can occur, forming ulcers that often have a foul smell and are accompanied by bleeding. Breast cancer can also extensively adhere to the skin. If cancer cells spread to the breast and the surrounding skin, multiple small nodules may appear and even fuse together. Lymph node metastasis is most commonly seen initially in the axillary region. In the early stages, the lymph nodes are scattered, enlarged, and hardened, but still movable. They then gradually increase in number and form hard lumps, and can even adhere to deep tissues and the skin. The lymph nodes above the collarbone can also become enlarged and hardened. The opposite axilla may also have lymph node metastasis. If cancer cells block the main lymphatic vessels in the axilla, it can cause lymphatic reflux obstruction in that arm, leading to arm edema; if the lymph nodes under the collarbone harden and compress the axillary vein, it may cause a purple edema in the arm on that side.