Symptoms of mid-stage breast cancer often include the breast becoming smaller and harder, the nipple being elevated, and, due to the involvement of the milk ducts, becoming flattened and retracted or even inverted. The breast can also significantly increase in size over a few months, causing the affected breast tissue to become enlarged and protrude. Breast cancer invades the pectoral muscles and their fasciae, making the tumor fixed to the chest wall and difficult to move. Cancer cells obstruct subcutaneous lymphatic vessels, causing lymphatic retention, which leads to dermal-edema-like swelling, and the skin appears with a characteristic peau d'orange (orange peel) texture. Lymph node metastasis initially appears in the axilla, starting as scattered enlarged and hardened lymph nodes that are still movable, then gradually becoming larger and forming hard masses, and even adhering to deep tissues and skin. The lymph nodes above the collarbone can also become enlarged and hardened. There could also be metastasis to the lymph nodes in the opposite axilla. If the cancer cells block the main lymphatic vessels in the axilla, it can cause lymphatic drainage issues in the arm on that side, resulting in a waxy, pale swelling of the arm.