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Types of Breast Cancer

There are many types of breast cancer, though some of them are very rare. The majority of breast cancers begin in the cells that line the ducts. Others begin in the lobules. A small number start in other tissues.

In this section, you will learn about in situ and invasive breast cancers. Occasionally a breast tumor may be a mix of these types.

In situ breast cancers

In situ — which translates to “in place” in Latin — means that the abnormal cells tend to be confined to the type of tissue where they develop and may be less aggressive than invasive cancers.

  • Ductal carcinoma in situ (DCIS), also known as stage 0, intraductal, or pre-invasive breast cancer, is the most common form of in situ breast cancer. According to Stanford Medicine, it accounts for about 20% of all newly diagnosed breast cancers. Although DCIS tends not to spread outside the ducts of the mammary glands, about 50% of cases can develop into more invasive cancers if left untreated. However, the outlook is usually excellent for people who receive treatment for DCIS.

  • Words to Know

    Biopsy is the removal and examination of tissue for the purpose of diagnosing disease.

  • Lobular carcinoma in situ (LCIS) technically is not cancer, although it has the word “carcinoma” in its name. Also called lobular neoplasia, LCIS occurs when abnormal cells grow in the breast’s milk-producing glands. LCIS can often be found in lobules throughout the breast. In about 30% of cases, both breasts are affected. About 25% of people who develop LCIS will develop breast cancer in the future. But because LCIS generally does not show up on mammograms or have symptoms, it is often diagnosed during a breast biopsy that’s being done for other reasons.

Invasive breast cancers

Invasive breast cancers spread to multiple parts of the breast and can eventually travel to nearby lymph nodes. From there, the cancer may travel through blood and the lymphatic system to other parts of the body, such as the bones, liver, or lungs.

Breast Cancer Animation

Watch a medical animation to see how invasive breast cancer develops.

  • Invasive (or infiltrating) ductal carcinoma (IDC) accounts for the majority of all breast cancers. It begins in the ducts, breaks through their walls, and can invade other parts of the breast when left untreated.
  • Invasive (or infiltrating) lobular carcinoma (ILC) is the second most common type of breast cancer, and accounts for about 10% to 20% of all cancers originating in the breast. It starts in the lobules, or milk glands, and can spread to other parts of the body. Because ILC advances from the lobules into nearby tissue in a web-like pattern, its initial symptoms may be a thickening or change in texture of the breast rather than a lump or mass.
  • Inflammatory breast cancer (IBC) accounts for about 1% to 3% of all breast cancers and affects the soft tissues of the breast. Rather than causing a defined lump or mass, IBC makes the breast feel warm, tender, and sometimes swollen and itchy. The skin may also appear thick and pitted. Because of its symptoms, IBC is often mistaken for an infection in its early stages.

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