Breast cancer can be classified in two broad categories: noninvasive and invasive.
Non-invasive or in situ breast cancers stay within the breast and do not spread into surrounding tissues.
Invasive or infiltrating breast cancers spread outside the breast into other parts of the body through blood and lymph nodes.
Breast cancer is also classified based on where in the breast the disease started and how the disease grows.
Invasive ductal carcinoma
This is the most common type of breast cancer, beginning in the lining of the milk ducts (thin tubes that carry milk from the lobules of the breast to the nipple).
Invasive lobular carcinoma
This cancer begins in the lobules (milk glands) of the breast. It is found in both breasts more often than other types of breast cancer.
Inflammatory breast cancer
In this uncommon type, the breast is red and swollen and may have thickening of the skin that resembles an orange peel.
Recurrent breast cancer
This is disease that returns after it has been treated. It may come back in the breast, in the chest wall or in other parts of the body.
Metastatic breast cancer
This is a breast cancer that has spread to sites and organs outside the breast and regional lymph nodes. One in 20 women are found to have metastatic cancer when they are first diagnosed with breast cancer. In others, spread is discovered after a previous diagnosis of early-stage breast cancer.