What are the common types of breast cancer?

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Ductal carcinoma in situ (DCIS) is considered a non-invasive or pre-invasive breast cancer. Ductal means that cancer begins within the milk ducts, carcinoma refers to any cancer that originates in the epithelium (including breast tissue) that lines or covers the internal organs, and in situ means "in its original place". The difference between DCIS and invasive cancer is that, in DCIS, cells do not infiltrate through the walls of the milk ducts into the surrounding breast tissue. DCIS is considered a 'pre-cancer', but in some cases it can develop into invasive cancers.

Ductal carcinoma in situ. Also known as an intraductal neoplasm, it is considered a precursor lesion or pre-invasive breast cancer. About 20% of new breast cancer cases are ductal carcinoma in situ. Almost all women diagnosed at this stage (in situ) of the disease can be cured when properly treated.

  Invasive (or infiltrating) ductal carcinoma is the most common type of breast cancer. About 80% of all breast cancers are invasive ductal carcinomas. Invasive ductal carcinoma refers to cancer that has ruptured the wall of the milk ducts and invaded the breast tissues. Invasive ductal carcinoma can spread to lymph nodes and possibly other areas of the body.

Invasive lobular carcinoma. Invasive lobular carcinoma starts in the milk-producing glands (acini/lobules) and accounts for about 10% of invasive breast cancers. It has a greater tendency to be multicentric (several foci) or bilateral (both breasts). It may be more difficult to diagnose by mammography than invasive ductal carcinoma.

Special Types of Invasive Breast Carcinoma

There are some special types of breast cancer, which are subtypes of invasive carcinoma. They are important as they represent different prognoses.

Adenoid cystic carcinoma.

Metaplastic carcinoma.

Medullary Carcinoma.

Mucinous Carcinoma.

Papillary carcinoma.

Tubular carcinoma.

Some subtypes have the same or perhaps worse prognosis than invasive ductal carcinoma, and include:

Metaplastic carcinoma.

Micropapillary Carcinoma.

Mixed carcinoma (has invasive lobular and ducal characteristics).

In general, all of these subtypes are treated as invasive ductal carcinoma.

Less Common Types of Breast Cancer

Inflammatory Breast Cancer. It is a rare type that accounts for about 1 to 3% of breast cancers. It is characterized by inflammatory signs and has a compromised dermis (orange peel skin) and usually does not cause a lump or mass in the breast. The affected breast may also be larger or firmer, tender or itchy. A rash or reddening of the skin is common. These changes are caused by cancer cells that block the lymph vessels in the skin. Inflammatory breast cancer usually has a rapid growth rate.

Paget's disease. This type of breast cancer starts in the breast ducts and spreads to the skin of the papilla and to the areola. It is rare, accounting for about 1% of breast cancer cases. It affects the papillary ducts first and then spreads to the papillary surface and areola. A scaly, red, itchy, and irritated papillary areolar complex are signs of Paget's disease in the papilla. One hypothesis for the cause of Paget's disease is that cancer cells begin to grow inside the milk ducts in the breast and then penetrate the surface of the papilla. Another possibility is that the papilla cells become cancerous.

Malignant phylloid tumor. It is a very rare type of breast tumor, corresponding to 2% of tumors, which develops in the stroma (connective tissue) of the breast, in contrast to carcinomas, which develop in the ducts or lobes.

Fibroepithelial of the breast, mixed lesions, with 80% of cases represented by benign tumors

Angiosarcoma. This type of cancer starts in the cells that line the blood vessels or lymph vessels. It rarely occurs in the breast, but they are very aggressive

Triple-negative breast cancers are tumors that test negative for estrogen receptors (ER-), progesterone receptors (PR-), and HER2 (HER2-) in a pathology report. These negative results indicate that cancer growth is not supported by the hormones estrogen and progesterone, nor by the presence of many HER2 receptors.