Breast cancer's appearance under microscope is categorized into two major groups with two totally different behavior patterns:

Invasive

Breast cancer refers to the most common type of breast cancer.

• Infiltrating ducal carcinoma - Most breast cancers are of this type.
• Infiltrating lobular carcinoma- 10% of breast cancers are of this type.

Non-Invasive

There are primarily two types of breast cancer to be found in most women. These types of breast cancer are named after the parts of the breast in which they start. They are:

1. Ductal Carcinoma Breast Cancer
   
   It starts in the cells which line the breast's ducts, beneath the nipple and areola. The ducts supply milk to the nipple. Between 85% and 90% of all breast cancers are ductal. If the cancer is DCIS (ductal carcinoma in situ), it is well contained, not invasive, and can be very successfully treated. Usually removed during a lumpectomy, if the tumor margins are clear of cancer, follow-up treatment may include radiation. If ductal cancer has broken into nearby breast tissue (invasive cancer) then a mastectomy may be needed, and your physician may also recommend chemotherapy.
2. Lobular Carcinoma Breast Cancer
   
   It begins in the lobes or glands which produce milk in the breast. The lobes are located deeper inside the breast, under the ducts. About 8% of breast cancers are lobular. If the cancer is LCIS (lobular carcinoma in situ) that means the cancer is limited within the lobe and has not spread. It may be removed during a lumpectomy, if the tumor margins are clear of cancer, and follow-up treatment may include radiation. If lobular cancer has spread into nearby breast tissue (invasive cancer) then a mastectomy may be needed, and your physician may also recommend chemotherapy.

Types of Breast Cancer

One of the rarest forms of breast cancer is named for its appearance.

• Inflammatory Breast Cancer
  
  It is the least common, but most aggressive of breast cancers, taking the form of sheets instead of lumps. The breast may feel warm, and be red and swollen. It can also feel tender or itchy. It can start in the soft tissues of the breast, just under the skin, or it can appear in the skin. Unlike ductal and lobular cancers, it is treated first with chemotherapy and then with surgery. When caught early, inflammatory breast cancer can be a manageable disease and survival rates are increasing. But because there are usually no lumps the cancer often isn't detected until it has progressed.

Least common is cancer of the nipple, named for Sir James Paget who first noticed the relationship between changes in the nipple and the underlying breast cancer.

• Paget's Disease of the nipple/areola
  
  It often looks like a skin rash, or rough skin. It resembles eczema, and can be itchy. The itching and scabs (if scratched) are signs that cancer may be under the surface of the skin, and is breaking through. Paget's is usually treated with a mastectomy, because the cancer has by then invaded the nipple, areola, and the milk ducts.