After puberty, a woman's breast consists of fat, connective tissue, and thousands of lobules, tiny glands that produce milk for breast-feeding. Tiny tubes, or ducts, carry the milk toward the nipple.
nvasive breast cancer is when the cancer cells break out from inside the lobules or ducts and invade nearby tissue, increasing the chance of spreading to other parts of the body.
The first symptoms of breast cancer are usually an area of thickened tissue in the breast, or a lump in the breast or in an armpit.
The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Breast cancer can also begin in the cells of the lobules and in other tissues in the breast. Ductal carcinoma in situ is a condition in which abnormal cells are found in the lining of the ducts but they haven't spread outside the duct. Breast cancer that has spread from where it began in the ducts or lobules to surrounding tissue is called invasive breast cancer. In inflammatory breast cancer, the breast looks red and swollen and feels warm because the cancer cells block the lymph vessels in the skin.