Breast tissue can develop abnormalities. Sometimes these abnormalities are cancerous and sometimes they are not. A breast abnormality is usually referred to as a lump.
A lump in the breast can be made of normal cells or cancer cells. A lump may be found using mammography, ultrasound or MRI or felt during a breast exam (by your doctor or you). Once a lump is found, a biopsy can be done to remove pieces of the tissue from it to determine if there are cancer cells present.
Cancer cells are cells that are abnormal and grow in an uncontrolled way. They may stay in the place where they started to grow, or they may grow into the normal tissue around them. Usually breast cancer begins either in the cells of the lobules, which are the glands that produce milk, or in the ducts, which are the passages that drain milk from the lobules to the nipple. Cancer cells can also spread beyond the breast into other parts of the body.
Non-invasive cancers stay within the milk ducts or milk lobules. They do not grow into or “invade” the normal tissue within or beyond the breast. Non-invasive cancers are sometimes called in situ.
If the cancer has grown into normal tissues, it is called invasive. Most breast cancers are invasive. Sometimes cancer cells spread to other parts of the body through the blood or lymph system. When cancer spreads to other parts of the body it is called Metastatic breast cancer.
The Most Common Types of Breast Cancer
DCIS – Ductal Carcinoma In Situ. This cancer is non-invasive; it stays within the milk ducts. DCIS is considered the earliest form of breast cancer.
LCIS – Lobular Carcinoma In Situ. This cancer is non-invasive; it stays within the milk lobules. LCIS usually doesn’t show up on mammograms; the condition is most often discovered as a result of a biopsy done for another reason, such as a suspicious breast lump or an abnormal mammogram. Women with LCIS have an increased risk of developing invasive breast cancer.
IDC – Invasive Ductal Carcinoma. This is a cancer that began in the milk duct but has grown into the surrounding normal tissue within the breast. This is the most common kind of cancer; about 80% of all breast cancers are invasive ductal carcinomas. Sometimes IDC is called infiltrating ductal carcinoma.
ILC – Invasive Lobular Carcinoma. This is a cancer that began in the milk lobule but has grown into the surrounding normal tissue within the breast. ILC typically doesn’t form a lump, as most women expect with breast cancer. Instead, ILC more often causes a thickening of the tissue or fullness in one part of the breast.
Other, Less Common Types of Breast Cancer
Inflammatory Breast Cancer. Inflammatory breast cancer is a very rare (found in 1%-5% of breast cancers diagnosed) but aggressive form of breast cancer. It presents itself with swelling, a feeling of heat inside the skin, a red hue to the breast area and the breast sometimes swells up too. Often this is often initially misdiagnosed as mastitis, which is a breast infection. Inflammatory breast cancer occurs when cancer cells block the lymphatic vessels in the 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.
Medullary carcinoma. This is a form of invasive ductal carcinoma but it is found in only 3%-5% of all breast cancers diagnosed. Medullary carcinoma of the breast may not always feel like a lump, but rather, like a thick, spongy area of breast tissue. This type of breast cancer can produce swelling from within your breast. The cells for medullary carcinoma are large and tend to stay together and expand in one place.
Phyllodes. Phyllodes are very rare tumors, accounting for less than 1% of all breast tumors. Phyllodes tumors tend to grow quickly, but they rarely spread outside the breast. Although most phyllodes tumors are non- cancerous, some are cancerous.