You're facing your worst fear: Your doctor says you have breast cancer. As this news slowly sinks in, you'll probably have many questions related to your diagnosis and treatment options.

Two factors are key as you discuss your condition with your doctor:

• What type of breast cancer you have
• What stage your breast cancer is in

Both your breast cancer type and stage dictate which treatment options, including surgery, chemotherapy, hormone therapy and radiation, offer the best chance of a cure in your situation.

The two most common types of breast cancer are defined by their place of origin from within the breast:

• Ductal carcinoma — the cancer starts in one of your milk ducts.
• Lobular carcinoma — the cancer originates in a milk-producing lobule of your breast.

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Female breast anatomy

These two types of cancer are further broken down by whether or not they've spread to other parts of your body. In situ cancers are those that have remained in place and haven't invaded tissues beyond the duct or lobule. Invasive (infiltrating) cancers have spread beyond the duct or lobule into the surrounding tissues that support the ducts and lobules of your breast. You may find that you have one of the following:

• Ductal carcinoma in situ (DCIS). A diagnosis of DCIS means that abnormal cells are in the lining of a milk duct in your breast, but they haven't invaded surrounding breast tissue. This is an early-stage breast cancer — so early, in fact, that some consider DCIS a precancerous condition. Almost all women with DCIS can be successfully treated. However, if left untreated, DCIS may develop into invasive breast cancer.
• Lobular carcinoma in situ (LCIS). If your doctor describes your cancer as lobular carcinoma in situ, it means that abnormal cells are in a lobule of your breast, but they haven't invaded surrounding breast tissue. Many experts don't classify LCIS as a cancer at all but consider it a marker for the future development of cancer. If you have LCIS, you're at an increased risk of developing invasive cancer, either lobular or ductal, sometime in the future. Invasive cancer could occur in either of your breasts, regardless of which breast the LCIS was found in.
• Infiltrating ductal carcinoma (IDC). This breast cancer accounts for as many as four out of five invasive breast cancers. If you have IDC, cancer cells form in the lining of your milk duct, break free of the duct wall and invade surrounding breast tissue. The cancer cells may remain localized — staying near the site of origin — or they can spread (metastasize) even further throughout your body, being carried by your bloodstream or lymphatic system.
• Infiltrating lobular carcinoma (ILC). Although it's less common than IDC, this type of cancer acts in a similar manner. It starts in the milk-producing lobule and invades the surrounding breast tissue. It can also spread to more distant parts of your body. If you have ILC, you might not be able to detect a breast lump. You may perceive only a general thickening — or a sensation that your breast tissue feels different — in an area in your breast. ILC may be harder to detect by touch, and it's also less likely to appear on a mammogram.

Your doctor might tell you that you have neither ductal nor lobular carcinoma, but you do have breast cancer. In that case, you may have a less common type of breast cancer. These include:

• Inflammatory breast cancer. This is a rare but aggressive type of cancer. With inflammatory breast cancer, the skin of your breast becomes red and swollen and may take on a thickened, pitted appearance. This results from cancer cells blocking the lymph drainage from the skin on your breast.

• Medullary carcinoma. This is a specific type of invasive breast cancer characterized by a well-defined division between cancerous tissue and noncancerous tissue, the large size of the cancer cells and the presence of immune system cells around the border of the tumor.
• Mucinous carcinoma. With this type of invasive breast cancer, the cancer cells produce mucus and grow into a jelly-like tumor. The prognosis for mucinous carcinoma is better than for other, more common types of invasive breast cancer.
• Paget's disease of the breast. This rare type of breast cancer affects your nipple and the dark area of skin surrounding your nipple (areola). It starts in a milk duct, as either an in situ or invasive cancer. If associated with carcinoma in situ, the prognosis is very good.

Your breast cancer may come back after you've been treated. It may recur in your breast or the soft tissue of your chest (chest wall), or it may appear in another part of your body — such as your lungs, liver or bones. When breast cancer returns in this manner, it is known as recurrent breast cancer. Your treatment options depend on:

• Past treatments
• Where the cancer has spread
• Characteristics of the tumor cells, such as hormone receptor status
• Age
• Menopausal status
• Overall health

If you've had breast cancer in the past and you notice any changes in your breasts, see your doctor as soon as possible.