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Invasive (Infiltrating) Breast Cancer

Types and Subtypes of Invasive Breast Cancer

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Updated April 26, 2011

There are more than 100 types and subtypes of breast tumors, according to the World Health Organization. Invasive, or infiltrating, breast cancer is diagnosed when cancer cells that started in your milk ducts or lobes spread to, or invade, healthy surrounding tissue. Invasive breast cancer has the potential to travel to other parts of your body through your bloodstream and lymph system.

Some breast tumors are harmless, such as fibroadenomas and intraductal papillomas. Other early stage breast tumors are harmful but well contained to the tumor site, and these are ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). There are many types of invasive breast cancers and here are the most common types:

Invasive ductal carcinoma (IDC) - This is the most common type of breast cancer. It starts in your milk ducts, then breaks out and invades nearby breast tissue. Here are some subtypes of invasive ductal carcinoma:

  • Inflammatory breast cancer (IBC) - This is an advanced, aggressive form of cancer, which starts out in the milk ducts and proceeds to invade the skin and lymph system. IBC does not signal its presence with a breast lump, but with breast pain and skin changes and is often mistaken for other breast conditions. Most cases of IBC can be detected by a mammogram or an ultrasound.
  • Medullary carcinoma - named for its resemblance to brain (medulla) tissue, this subtype of IDC is generally good.
  • Metaplastic breast cancer - a rare form of breast cancer that is often treated aggressively and has uncertain prognosis.
  • Paget's disease of the nipple - shows up in and around the nipple and usually signals the presence of breast cancer beneath the skin.
  • Tubular carcinoma - a rare type of breast cancer, it takes its name from its microscopic appearance and has a better prognosis than most forms of invasive breast cancer.
Invasive lobular carcinoma (ILC) - Lobular breast cancer begins in your milk-producing glands or lobes. When it leaves your lobes and infiltrates fatty tissue and other breast tissues close to the lobes, it becomes invasive.

Papillary Carcinoma - This is a type of ductal carcinoma in situ (DCIS). This type of breast cancer is rarely invasive and usually stays within the milk ducts of your breast.

Less Common Invasive Breast Cancer Types

Each of these types of breast cancer occur in less than 5% of all cases that are diagnosed.
  • Adenoid cystic carcinoma - Named for their microscopic appearance, these cancer cells resemble glandular and cystic cells. Usually not aggressive, this type of breast cancer has a good chance of recovery after treatment.
  • Mixed tumors - Tumors that are composed of different types of cancer cells, such as invasive ductal and lobular, are referred to as mixed tumors.
  • Mucinous (colloid) carcinoma - Quite rare, this type of breast cancer produces mucous but has a good prognosis after treatment.
  • Sarcomas of the breast - Sarcomas are cancers that form in connective tissue. Most breast cancers are carcinomas, which form in epithelial tissue.
    • Angiosarcoma - This rare type of breast cancer starts in cells that line the blood vessels within your breast or underarm area. It can occur due to radiation treatments and is apt to grow and spread quickly.
    • Phyllodes tumor (cystosarcoma phyllodes) - Named for its leaf-shaped growth pattern, these tumors are often harmless. If they are cancerous, surgery is required, but a Phyllodes tumor will not benefit from chemo or radiation treatments.

    Sources:
    Tumours of the breast and female genital organs, World Health Organization classification of tumours, 2003, ISBN 92 832 2412 4.

    American Cancer Society. What is Breast Cancer? Revised: 09/13/2007.

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