Inflammatory breast cancer is a rare type of breast cancer that develops rapidly, making the affected breast red, swollen and tender. Inflammatory breast cancer occurs when cancer cells block the lymphatic vessels in skin covering the breast, causing the characteristic red, swollen appearance of the breast. Inflammatory breast cancer is considered a locally advanced cancer — meaning it has spread from its point of origin to nearby tissue and possibly to nearby lymph nodes. Inflammatory breast cancer can easily be confused with a breast infection, which is a much more common cause of breast redness and swelling. Seek medical attention promptly if you notice skin changes on your breast.